Muffin-Pan Potato Gratins

2 medium russet potatoes (about 3/4 pound each)
dried rosemary
6 Tbsp heavy cream

Preheat oven to 400. Spray 6 standard muffin cups with cooking spray. Thinly slice potatoes. Place 2 slices in each up and season with coarse salt, ground pepper and rosemary. Continue adding potatoes, seasoning every two slices, until cups are filled. Pour 1 tablespoon heavy cream over each. Bake until potatoes are golden brown and tender when pierced with a knife, 30-35 minutes. Run a thin knife around each gratin. Place a baking sheet or large plate over pan and invert to release gratins. Flip right side up and serve.