Preheat oven to 350 degrees
Peel all your potatoes. You'll want to trim their width down a bit to make sure your little circles fit into the muffin pan so just slice off the slices and try to shape the potato into a circle/cylinder a bit. You won't get it perfect and you dont have to worry about that. It will look more like an octagon.
Using a mandoline or a very sharp knife, slice your potatos into 2mm or 1/10" slices. Add to a bowl and set aside.
Let's make the sauce. Melt the butter over a saucepan over medium heat. Once melted, add in the garlic and stir for 1 minute. Add in oregano, thyme, salt and heavy cream. Cook for 1 minute and remove from heat.
Time to make your stacks! Spray your muffin tin with non stick spray.
Place potato circles into your muffin tin about halfway up the tin holes.
Add 1 tsp of the creamy sauce onto each potato stack. You'll use half the cream mixture.
Add the gruyere cheese on top of each stack. Use all of your gruyere cheese.
Top each stack with remaining potato slices. Their height should go above the muffin tin (they're going to shrink in the oven).
Drizzle with the remaining cream mixture.
Cover loosely with foil and bake for 40 minute.
Remove from oven and sprinkle with the parmesan cheese. Use all your cheese. Return to the oven without foil and bake for 10 minutes or until that cheese is nice and golden.