Preheat the oven to 375 degrees F and grease a 12-cup muffin tin.

Cut the puff pastry into squares and press one into each cup.

Whisk the eggs, milk, salt, and pepper together.

Divide the ham, cheese, and chives among the pastry cups.

Pour the egg mixture over each until three-quarters full.

Bake 20 minutes, until puffed and set, then cool 5 minutes before removing.