I check the weather at the beginning of each week to see which day will be best for my solar oven cooking adventures, and I start planning what I will cook for that day.  (Now if I would just do that kind of planning for every day of the week, dinner would be a snap!)


I had some leftover ham from Mother’s Day dinner so I decided to make one of my kids’ favorite “meals:” au gratin potatoes with ham in them.  It seems like it always takes so long to make these (i.e. bake them so they are actually cooked through) that if I don’t plan ahead, it never gets done.  But I figured if they sat for hours in a solar oven, they would certainly get cooked through, wouldn’t get burned, and would be a great test of the whole solar oven process.


To be honest, I never really use a recipe for au gratin potatoes because it’s just ratios and basic cooking.  But I want you to know that I actually measured and took notes so I could give you a delicious recipe that you could replicate!  But remember, a recipe is just a jumping off point–you can adapt it to fit your own tastes and ingredients you have on hand.  Stay with me; it’s going to be amazing…


Here’s my “Sun Oven” solar oven cooking adventure for the week:

0)  I set the Sun Oven solar oven outside to preheat.

1)  Back inside, I melted some butter, added diced onion and minced garlic and sautéed it all on medium-low for 3-4 minutes.  (Remember, the detailed recipe follows.)
Butter, onion, and garlic sauteing in a pot to make a roux for au gratin potatoes

2)  I stirred in some flour, and cooked and stirred for 1 minute to make a roux of sorts.

3)  I whisked in the chicken stock.

4)  I whisked in the milk, salt, ground black pepper, and dried parsley flakes.  Turning up the heat to medium-high, I cooked and stirred constantly until the sauce thickened and began to simmer.  I reduced the heat to medium-low and simmered and stirred for 1 minute more.  Removed from heat and set aside.
Four photos showing a roux, adding broth, milk, and herbs to make sauce for au gratin potatoes


5)  I scrubbed and peeled (if desired) potatoes and sliced into 1/8-inch thin slices.  I used 3 ½ pounds, and that was a bit too many for my pot.  If you don’t have a kitchen scale, you can eye-ball it by counting out how many whole potatoes will cover the bottom of your pan, then adding half that many more potatoes.  This should make two layers.  (I started with too many!)
A pile of scrubbed peeled and sliced potatoes that have been sliced very thinly for au gratin potatoes

How to eyball figure out how many potatoes to use for au gratin potatoes if you don't have a kitchen scale

If you don’t have a kitchen scale, you can just eyeball how many potatoes to use.


6)  I greased the bottom and sides of a 2-qt casserole dish (black enamel for solar oven).  I always pour in just enough sauce to cover the bottom with a thin layer.  (This is the magic step that ensures you will be able to scrape that last delicious bite out of the pan because it won’t be burned on.)  Then I spread half the potato slices on top of the sauce, covered them with half of the remaining sauce, some grated cheddar cheese (and some diced ham if you like).
Spread a thin layer of sauce onto the bottom of the casserole dish before you layer the potatoes for au gratin potatoesThree photos showing how to layer potatoes and sauce for au gratin potatoesThree photos showing how to layer cheese, ham, and finish for making au gratin potatoes

7)  Then I repeated the layers with the remaining potatoes and sauce, spreading the top layer of sauce to cover all exposed potatoes.  I finished by sprinkling the top with the remaining ¼ C cheese.

8)  My Sun Oven solar oven was preheated to 350°F by 9:00 a.m., and it was only 50°F outside.  Nice.  A very clear day (no haze, no clouds) makes a difference in how hot the oven gets, regardless of the outside temperature.  I carefully set the covered pan of potatoes in the solar oven and sealed the door.  An hour later is was still 350°F in the oven and 55°F outside.
Sun Oven solar oven cooking with a black enameled pot cooking inside, plus a steamed up solar oven window glass

Ninety minutes later the glass had steamed up, so the temperature had dropped to 300°F.  I opened the door quickly and wiped it with my sleeve.  It was hot!  Maybe don’t do that again.


But the time I was done with my yard work (3 ½ hour total), the solar oven’s temperature had dropped to 275°F because of the interior steamed-up window.  It’s like a cloud inside the oven, and it has a similar effect as a cloud outside the oven: it doesn’t let as much sunlight in, so the oven can’t get as hot.


I had no idea what to expect when I pulled the lid off.  I was hoping it wasn’t a big, soupy mess.  This is what I found:
Solar Oven Cooking - Finished au gratin potatoes that were baked in a Sun Oven solar ovenWow!  I was blown away by the results.  Did I mention that it just happened to be lunchtime?  I know what I’m having.


I was going to eat while I finished up some notes on this solar oven adventure, but I just couldn’t.  These potatoes were so amazing I just had to savor every bite without distraction.


Here’s what I learned today:  There was a bit too much soupy cheese sauce in the bottom of my pan after cooking in the solar oven.
Sun Oven solar oven-baked au gratin potatoes that are a little juicyThis is probably a combination of three factors: my layers of potatoes were really thick, i.e. I used too many potatoes that released too much of their own moisture; the baking lid had to be on the entire time, thus keeping extra moisture in; the solar oven door is sealed and doesn’t let moisture escape.  Next time I will reduce the potato amount and possibly even the sauce amount, although I felt the recipe had the perfect amount of sauce.  And really, the soupy cheese in the bottom wasn’t that big of a deal. This is “emergency cooking” after all, and I wasn’t feeding the Queen.  (Your results will be totally different with a conventional oven, because you won’t use so many potatoes, and the foil covering your dish will only be on half the time it bakes.  See recipe below.)


I always let the solar oven cool off, with its glass door open, in the shade or indoors after I’ve used it.  It appears the oven’s thermometer had a problem with all that steam today:
The Sun Oven solar oven internal thermometer seems to be a little foggy after useI wonder if anyone else has had this problem?



Here’s the recipe I promised you.  While I can’t promise to follow it perfectly in the future :) I can promise you that it made some of the most amazing au gratin potatoes I have ever eaten.  Enjoy!


Au Gratin Potatoes

(that you can bake in a conventional oven ~or~ a solar oven!)
Makes a 3-quart (9”x13”) pan, approximately 10-12 servings

6 Tbs. butter
1/3 Cup diced onion
1 large clove minced garlic
6 Tbs. white flour

1½ Cup stock or broth of your choice
1½ Cup milk
1 tsp. salt
½ tsp. ground black pepper
1 Tb. dried parsley flakes

4 pounds potatoes, scrubbed, peeled if desired, sliced in 1/8-inch thin slices
1½ Cup grated cheddar cheese
(1½ Cup cooked, diced ham, if desired)
More dried parsley flakes for the top

(A note about salt:  Dairy products [butter, milk, cheese] are naturally salty, as is salt itself.  If you also add salted stock and ham, you are adding even more salt flavor.  Take this into consideration with your own salt preferences as you prepare this dish.)


–(Begin by setting your solar oven out to preheat.)
–Finely dice the onion and mince the garlic.
–Melt the butter on medium-low heat, add the onion and garlic, and sauté for 3-4 minutes.
–Stir in the flour and cook and stir one minute more.
–Whisk in the stock/broth.  Whisk in the milk, salt, pepper, and parsley flakes.
–Increase the temperature to medium-high and cook and stir constantly until the mixture starts to thicken and bubble.  Reduce heat to medium-low and cook and stir constantly for one minute more.
–Set the sauce aside.
–Pre-heat your conventional oven to 400°F.
–Wash, peel (if desired), and slice the potatoes into thin 1/8” slices.
–Spray with non-stick spray the bottom and sides of a 9”x13” (3-quart) casserole dish.
–Pour a thin layer of sauce into the dish and spread to cover the bottom surface.
–Layer into the dish half the potatoes, (ham if desired), half the remaining sauce, and 1 cup of the cheese.
–Repeat the layers of potatoes, sauce (making sure to spread the top layer of sauce to cover every exposed potato), and cheese.  Sprinkle on some parsley flakes if desired.
–Lightly cover your dish with foil that has been sprayed with non-stick spray and bake it for 30 minutes in your 400°F oven, then uncover it and bake it for 30 minutes more.  Poke a fork into the center to test for doneness.
–(OR cover it with a lid and place it in your solar oven and adjust the time accordingly – my solar oven has never reached 400°F, so I bake it longer.  Using foil in a solar oven isn’t a good idea because it reflects the heat right back out.)

FYI, I used a 2-qt, covered, black enameled dish in the solar oven, so I “two-thirds” the above recipe so it would fit.  Adjust the recipe according to your dish size.

Enjoy your delicious au gratin potatoes, from the solar oven or your conventional oven!


Other posts in this series:

Solar Oven Saturday – Intro
Solar Oven Saturday #1 – Roast Chicken
Solar Oven Saturday #2 – Homemade Bread
Solar Oven Saturday #4 – Banana Bread
Solar Oven Saturday #5 – Strawberry Rhubarb Crisp
Solar Oven Saturday #6 – Banana Blueberry Muffins

1 Comment
  1. Edith

    This is one of my favorite foods, just so good hot and cheesy.

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