01 - Preheat oven to 400°F (200°C). Generously butter a 12-cup muffin tin.
02 - Combine heavy cream, whole milk, minced garlic, sea salt, black pepper, and nutmeg in a small saucepan. Warm gently over low heat until steaming, then remove from heat.
03 - Arrange half the potato slices evenly among the muffin cups, overlapping slightly.
04 - Spoon a small amount of the warm cream mixture over the potatoes and sprinkle with half the grated cheese.
05 - Layer remaining potato slices on top of the first layer in each muffin cup.
06 - Top each portion with the remaining cream mixture and cheese. Drizzle melted butter over each mini gratin.
07 - Cover tin loosely with foil and bake for 25 minutes. Remove foil and bake an additional 15 minutes, until gratins are golden and bubbling.
08 - Let cool for 5 minutes. Gently loosen each gratin with an offset spatula and lift from the tin. Garnish with chopped chives or parsley if desired.