Begin by rolling out your pie dough on a lightly floured surface. Cut out 4-inch circles using a cookie cutter or a glass, then gently press each circle into the greased muffin tin cups. Freeze for 15 minutes.

Preheat your oven to 375°F (190°C).

In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, salt, pepper, and optional cayenne until well combined. Fold in the spinach, onion, ham, and Swiss cheese.

Carefully fill each dough-lined cup almost to the top with the egg mixture, leaving about 1/4 inch of space.

Bake for 25-30 minutes until the centers are set and edges are golden brown.

Remove from the oven and cool in the tin for about 10 minutes, then gently run a butter knife around the edges to release them.