Preheat and Prepare: Adjust your oven rack to the middle position and preheat the oven to 325°F (160°C). Prepare a 12-cup silicone muffin mold or a standard metal 12-cup muffin pan by coating the insides thoroughly with nonstick spray or butter. If using a metal pan, place the pan inside a larger baking dish or roasting pan that is large enough to create a water bath (Bain-Marie).

Blend the Base: In a high-powered blender, combine the 12 large eggs, the cottage cheese, the heavy cream, kosher salt, black pepper, and cayenne pepper (if using). Blend on high speed for 30 to 60 seconds until the mixture is completely smooth and no lumps of cottage cheese remain. The mixture should look slightly frothy.

Mix in Cheeses: Pour the egg mixture into a large bowl. Gently stir in the shredded Gruyère cheese, the shredded Monterey Jack cheese, and the minced chives until evenly dispersed throughout the liquid.

Distribute Fillings: Place a small pinch of the cooked bacon crumbles or other desired solid fillings (such as chopped spinach or roasted red pepper) into the bottom of each prepared muffin mold.

Pour and Fill: Carefully pour the egg mixture evenly into the prepared molds, filling each cup almost to the top. The eggs will slightly expand during baking.

Set Up Water Bath (Crucial for Texture): If using a water bath, carefully pour about 1 inch of hot water (tap water is fine) into the larger outer baking dish. The water should surround the base of the muffin mold but should not be so deep that it sloshes into the egg mixture. If you are using a silicone mold placed on a baking sheet, you may skip the water bath, though the texture will be slightly less creamy.

Bake: Carefully transfer the baking dish (with the water bath) to the preheated 325°F (160°C) oven. Bake for 25 to 30 minutes. The egg bites are done when the centers are set, puffed slightly, and feel firm to the touch. They should not look wet or overly browned.

Cool and Serve: Remove the pan from the oven and carefully lift the muffin mold out of the water bath. Let the egg bites cool in the mold for about 5 minutes. The edges will contract slightly, making them easy to remove.

Storage: Use a small spatula or knife around the edge to gently pop the egg bites out of the molds. Serve warm immediately, or allow them to cool completely before storing them in an airtight container in the refrigerator for up to 4 days, or freezing them for longer storage.