Step 1: Preheat your oven to 325°F (160°C). Grease your muffin tin thoroughly with cooking spray or a little butter to ensure easy removal.
Step 2: In a large mixing bowl, whisk the eggs vigorously for 2-3 minutes until they are light, frothy, and slightly pale yellow. This aeration is crucial for achieving fluffy egg bites. You can use a blender for an even smoother consistency.
Step 3: Add the milk or cream to the whisked eggs and continue to whisk until fully combined. Season generously with salt and freshly ground black pepper.
Step 4: Divide your chosen add-ins (like cooked spinach, diced bell peppers, or crumbled bacon) evenly among the 12 muffin cups. Do not overfill, leaving room for the egg mixture and cheese.
Step 5: Pour the egg mixture over the add-ins, filling each muffin cup about two-thirds full. Gently stir with a spoon in each cup to ensure the add-ins are dispersed.
Step 6: Sprinkle the shredded cheese evenly over the top of each egg bite.
Step 7: Carefully place the muffin tin in the preheated oven. Bake for 18-22 minutes, or until the egg bites are set, puffy, and lightly golden brown around the edges. A toothpick inserted into the center should come out clean.
Step 8: Remove the muffin tin from the oven and let the egg bites cool in the tin for 5 minutes. Then, run a thin knife or spatula around the edges of each cup and carefully pop them out. Serve warm, or allow them to cool completely before storing.