Preheat your oven to 375°F (190°C) and generously spray a 24-cup mini muffin tin with non-stick cooking spray.
Prepare the pie crust by unrolling it on a lightly floured surface. Using a 2.5-inch round cookie cutter or drinking glass, cut out 24 circles from the pie crust.
Gently press each dough circle into the mini muffin cups, creating a small pastry shell. The edges should just come to the top of each cup. If the dough tears, simply pinch it back together.
Pre-bake the empty crusts for 5 minutes to help prevent sogginess, then remove from the oven and let cool slightly while preparing the filling.
Whisk together the eggs, cream, and milk in a large measuring cup or bowl until well combined. Add salt, pepper, and nutmeg, then whisk again until the mixture looks uniform.
Distribute your mix-ins and cheese evenly among the partially baked crusts. Each cup should be about 1/3 filled with solid ingredients.
Carefully pour the egg mixture into each crust, filling them about 3/4 full. Be careful not to overfill as they will puff up during baking.
Bake for 15-18 minutes until the quiches are puffed, golden around the edges, and just set in the center. They should have a slight jiggle but not look wet.
Let cool for 5 minutes in the pan before gently removing each quiche using a small butter knife to loosen the edges if needed.
Garnish with fresh herbs and serve warm or at room temperature.