Sweet Potato Stacks

0 Preheat oven to 400°F / 200°C.
1 Spray a 12-space regular-sized muffin pan with nonstick cooking spray or brush it with cooking oil. Set aside.
2 Melt butter in the microwave or on the stovetop. Whisk in grated garlic. Set aside to cool slightly.
3 Use a mandolin or very sharp knife to thinly slice the sweet potatoes. You can peel them first if you like, though it's not necessary. Aim for slices that are 1/16-inch thickness.
4 Place sweet potato slices in a large mixing bowl and pour butter over top. Add thyme leaves, salt, and black pepper. 
5 Gently stir everything together, making sure that a small amount of butter gets between most of the slices.
6 Stack the sweet potato slices up in the prepared muffin tin, filling each section all the way up to the top or slightly higher.
7 Bake, uncovered, until sweet potatoes are golden brown on top and very tender, 30 to 40 minutes (this will vary depending on the thickness of the sweet potato slices). 
8 Remove the muffin pan from the oven. If any of the sweet potato stacks have tipped over, use a spoon to gently nudge them back into place. Allow stacks to cool in the pan for 5 minutes before removing. 
9 Serve warm.