Phase 1: Preparing the Muffin Tin and Crusts

1. Preheat Oven & Prepare Tin: Preheat your oven to 375°F (190°C). Lightly grease a standard 12-cup muffin tin with non-stick cooking spray or a thin layer of butter. Even if your tin is non-stick, this extra step ensures easy removal.
2. Cut the Crusts: Unroll your refrigerated pie crusts onto a lightly floured surface. Using a round cookie cutter or the rim of a glass (typically 3.5 to 4 inches or 9-10 cm in diameter – test one in your muffin tin to ensure it comes up the sides sufficiently), cut out 12 circles from the pie dough. You may need to re-roll the scraps to get enough circles. If using homemade pastry, roll it out to about 1/8 inch thickness before cutting.
3. Line Muffin Cups: Gently press each dough circle into a muffin cup, ensuring it lines the bottom and comes up the sides. Try to make the edges as even as possible. If the dough tears, simply pinch it back together.
4. Optional – Blind Bake (for extra crispiness): For an even crispier crust, you can briefly blind bake the pastry shells. Prick the bottom of each pastry shell a few times with a fork. Line each with a small piece of parchment paper and fill with pie weights or dried beans. Bake for 8-10 minutes. Carefully remove the parchment and weights. This step isn’t strictly necessary for mini quiches but can improve crust texture. If skipping, proceed directly to preparing fillings.

Phase 2: Preparing the Fillings and Custard

1. Cook Bacon: If you haven’t already, cook the bacon slices in a skillet over medium heat until crisp. Remove from skillet and place on a paper towel-lined plate to drain. Once cool enough to handle, crumble or chop it into small pieces.
2. Sauté Aromatics & Spinach: In the same skillet (you can drain off excess bacon grease, leaving about a teaspoon), add the olive oil or butter if needed. Add the finely chopped onion (or shallots) and sauté over medium heat for 3-5 minutes, or until softened and translucent. If using fresh spinach, add it to the skillet and cook until wilted, about 1-2 minutes. If using frozen spinach, ensure it’s thoroughly thawed and squeezed of all excess moisture before adding to the skillet or directly to the quiche cups.
3. Prepare Egg Custard: In a medium bowl, whisk together the large eggs. Once lightly beaten, whisk in the heavy cream (or milk/half-and-half), salt, pepper, and the pinch of nutmeg (if using). Whisk until everything is well combined and smooth. Be careful not to over-whisk, as this can incorporate too much air and make the quiches overly puffy and then prone to collapsing.

Phase 3: Assembling and Baking the Mini Quiches

1. Layer Fillings: Evenly distribute the prepared fillings among the 12 pastry-lined muffin cups. A good order is:

   • A sprinkle of crumbled bacon at the bottom.
   • A layer of the sautéed onion and spinach mixture.
   • A generous sprinkle of your chosen shredded cheese over the fillings.
   • Tip: Don’t overfill with solid ingredients, as you need room for the egg custard. About 1/2 to 2/3 full with solids is a good rule of thumb.

2. Add Egg Custard: Carefully pour or ladle the egg custard mixture over the fillings in each muffin cup, filling them almost to the top of the pastry. Leave a little space, as the egg will puff up slightly during baking.
3. Bake: Place the muffin tin in the preheated oven. Bake for 20-25 minutes, or until the egg custard is set (a knife inserted near the center should come out clean or with moist crumbs, not wet egg) and the tops are lightly golden brown. The crust edges should also be nicely browned.
4. Cool Slightly: Once baked, carefully remove the muffin tin from the oven and place it on a wire cooling rack. Let the mini quiches cool in the tin for at least 5-10 minutes. This helps them set further and makes them easier to remove without breaking.
5. Remove and Serve: Gently run a thin knife or small offset spatula around the edge of each quiche to loosen it, then carefully lift it out. Serve warm or at room temperature.