Pre-heat oven to 375 degrees F (190 C). Remove the pie crust from the freezer and bring it to room temperature to allow for easy rolling.
When ready, gently press the pie crust into a 9-inch tart pie pan. Allow for a couple of inches to extend beyond the sides of the tart or pie pan. Cover the bottom of the pastry with parchment paper and then add enough dried beans or peas to partly fill the pie pan. Bake for about 8-10 minutes, so that it does not puff up as it bakes. Set aside.
If making a mini quiche, place flat on a cutting board the crust. Then cut with a 2 1/2-inch round cutter, cut about 5-6 pieces from the crust. Press round into the bottom and upsides of each muffin cup.
Place the saucepan or skillet on medium-high heat, then add bacon, saute until crispy about 6-7 minutes. Drain any excess grease. Reserve about 1-2 tablespoons bacon grease.
Spread half of the bacon at the bottom of the pie crust.
Saute onion, garlic, and mushroom in the skillet with the reserve bacon grease (replace with butter), until wilted about 2-3 minutes – set aside and let it cool.
In a medium bowl, whisk together the eggs, heavy cream, and milk. Add to the cooldown onion-garlic mixture, and stir in the Creole seasoning.
Throw in the drained spinach and cheese, lightly mix. Adjust for seasonings with salt and pepper.
Carefully pour the egg mixture into the pie shell. Top with the remaining bacon.
Bake at 375 degrees F (190C) for about 50- 60 minutes, until the center is no longer wiggly. If the crust starts to get too brown, cover the edges with foil paper. For the mini quiche in a muffin pan, bake them for about 20 -25 mins.
Let the quiche cool and set for about 10 minutes before cutting into slices and serving.