How to Make It
Preheat oven to 375°F. Stir together cheeses, eggs, butter, and salt in a large bowl until combined. Stir in pasta and any other fillings, if desired, until combined.
Divide pasta mixture among 12 muffin cups, lightly coated with cooking spray. Bake in preheated oven until set and lightly golden around edges, about 15 minutes.