Creating Cheesy Mini Gratin Dauphinois Potato Stacks is straightforward if you follow these clear steps:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Prepare Potatoes: Peel the russet potatoes. Using a mandoline slicer or sharp knife, slice the potatoes thinly (about 1/8-inch thick).
3. Mix Cream and Seasoning: In a bowl, combine the heavy cream, minced garlic, salt, pepper, and nutmeg (if using). Whisk to combine.
4. Layer Potatoes: In a 12-cup muffin tin, start layering the potato slices. Place a slice in each muffin cup, then pour a small amount of the cream mixture over the slice.
5. Add Cheese: Sprinkle some Gruyère cheese over the potato layer. Repeat this process, creating successive layers until the cups are full, finishing with a slice of potato and a final drizzle of cream.
6. Top with Cheese: Sprinkle the remaining Gruyère and Parmesan cheese generously on top of each stack.
7. Bake: Place the muffin tin in the preheated oven. Bake for 45-50 minutes, or until the potatoes are tender and the top is golden and bubbly.
8. Cool Slightly: Once out of the oven, let the stacks rest for about 5 minutes. This helps them hold their shapes when removed from the tin.
9. Remove from Muffin Tin: Carefully use a small spatula or knife to lift the gratin stacks out of the muffin tin.
10. Garnish and Serve: Sprinkle with fresh thyme or chives for added flavor and visual appeal before serving.

These steps will guide you through the creation of these mouthwatering stacks effortlessly!