Preheat the oven to 350 degrees F. Spray 2 muffin tins with nonstick spray.
Thinly slice the potatoes to be about ⅛ inch thick. I use my mandolin for this but you can also use a knife! Place the potatoes in a large pot.
Pour the cream and milk over the potatoes. Add the garlic, salt, pepper, sage, thyme and nutmeg. Bring the mixture to a simmer over medium heat. Simmer, until fork tender, about 8 to 10 minutes.
Now it’s time to fill the muffin tins! Use a slotted spoon or kitchen tongs to place a few slices of potatoes into the first muffin tin. Sprinkle some cheese on top - a mix of the fontina and gruyere. Add another layer of potatoes over top, then another sprinkling of cheese. Use a spoon or small measuring cup to scoop some cream from the pot of potatoes. Stream it into the muffin tin, filling it ¾ of the way full to the top. Top with more cheese if needed. You can see my photos above!
Repeat with all the muffin tins. The exact amount will depend on how thinly you slice your potatoes, but you should easily get 15 muffin tins of potatoes and cheese, up to 24 tins. You do not have to use all the cream in the pot! Only use enough to fill the muffin tins ¾ of the way full once they have the potatoes and cheese in them.
Place the pans in the oven and bake for 40 to 45 minutes. Remove and let cool slightly for 5 to 10 minutes) before taking the potatoes out of tins, using a knife around the edges if they are stuck. Garnish with fresh thyme!