Preheat oven to 375 degrees. Place nine mason jar lids upside down on a flat baking sheet. Spray inside the rim of the lid and the baking sheet inside the jar lid with non-stick cooking spray.
Roll crust as for a pie. Cut into 3.75 - 4" circles (one inch larger than your jar lids). Line each jar lid with pie crust. Put baking sheet in fridge to keep the crusts cool.
Prepare fillings, if needed.
In a medium bowl, whisk together eggs and milk. Add a little salt and pepper.
Add fillings to each pie crust. Only fill about ½ way leaving room for the egg mixture.
Pour egg mixture in each pie crust just below the rim. DO NOT fill to the top unless you have a very steady hand when putting it in the oven (learn from my mistakes) Gently move fillings with fork to remove any air bubbles.
Bake for 15-20 minutes until the center is set.
Notes
You can use store bought pie crust or try our Hot Water Pie CrustIdeas for fillings:
cooked meat (bacon, sausage, ham, pepperoni, etc.)
cooked seafood (crab, shrimp, lobster)
vegetables cooked or uncooked (if you like them crunchy don't pre-cook, if you want them a bit softer, cook them a little before adding to the custard mixture).