Start by washing the potatoes thoroughly and slice them into 1/4 inch thick pieces. Aim for uniform slices to ensure even cooking and a consistent texture.
Next, place the sliced potatoes into your Instant Pot. Add the vegetable stock to help them steam perfectly. Seal the lid and set the cooker to high pressure for 1 minute. If you don't have an Instant Pot, boiling the potatoes on the stovetop until they are soft works just as well.
Once the timer goes off, carefully release the pressure and remove the potatoes. Set them aside while you prepare the sauce. This step ensures the potatoes remain intact for layering.
In the Instant Pot, switch to sauté mode. Add the butter and let it melt. It's important to watch closely to avoid burning.
Now add the minced garlic and sauté for about 1 minute until fragrant. The aroma should fill your kitchen, signaling that you're on the right track!
Next, add the fresh thyme, heavy cream, and the grated cheddar cheese. Stir continuously until the cheese melts and the sauce becomes smooth. Be patient here; it’s the key to that creamy texture.
Now, take a casserole dish and start layering the cooked potato slices. Pour the cheesy sauce generously over each layer. Don't be shy—this sauce is the heart of the dish!
After layering, top with additional grated cheddar cheese for that gooey, bubbly finish that everyone loves.
Finally, broil in the oven for about 5 minutes or until the top is golden and bubbling. Keep an eye on it, as broiling can go from perfect to burnt quickly!