Roll out the pie crusts on a lightly floured surface and cut out 4-inch circles. Grease a 12-cup muffin tin with butter and press dough circles into each cup.

Preheat your oven to 375°F (190°C).

In a large bowl, whisk together eggs, whole milk, and heavy cream. Add salt, pepper, and cayenne. Fold in spinach, onion, ham, and cheese.

Pour the egg mixture into each prepared muffin cup, filling them about three-quarters full.

Bake for 25-30 minutes until the tops are puffed and edges are golden brown.

Let cool for about 10 minutes before running a knife around the edges to release the quiches.