Preheat the Oven: Set your oven to 350°F (175°C). Lightly grease a muffin tin or use silicone liners.
Whisk the Eggs: In a mixing bowl, whisk the eggs until smooth. Season with salt and black pepper.
Add Fillings: Stir in the cooked breakfast sausage, shredded cheddar cheese, and chopped chives.
Fill the Muffin Cups: Pour the mixture evenly into a 6-cup muffin tin, filling each about ¾ full.
Bake: Place the muffin tin in the oven and bake for 18-20 minutes, or until the eggs are fully set and slightly golden on top.
Cool and Serve: Let the muffins cool for a few minutes before removing them from the tin. Enjoy warm, or store in the refrigerator for a quick grab-and-go breakfast.