01 -
Let's kick things off! Warm your oven to 375°F (190°C). This temp will make sure you get that nice golden top while keeping everything soft inside.
02 -
Now for the tasty part - drop your butter into a skillet on medium heat, then toss in those sliced onions. Let them cook slowly for about 15-20 minutes until they turn a lovely golden color and smell wonderful.
03 -
While your onions cook down, cut the potatoes into thin slices (around 1/8 inch thick). Mix them in a bowl with the heavy cream, then throw in some salt, pepper, and pull off some fresh thyme leaves.
04 -
Now comes the fun! Take a greased baking dish and put down half your creamy potato mix. Scatter half the browned onions on top. Do these layers again, then sprinkle all that yummy Gruyère over everything.
05 -
Put some foil over your dish and bake for 45 minutes. Then comes the best part - take off that foil and let it cook another 15-20 minutes until it's bubbling hot with a golden brown top.