Cooking spray or olive oil
8 ounces sugar-free uncooked pork breakfast sausage, casings removed
1 cup thinly sliced cremini mushrooms (about 3 ounces)
1/2 cup diced yellow onion
1 cup baby spinach (about 1 ounce), coarsely chopped
8 large eggs
3 tablespoons ghee, melted and cooled
1 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Arrange a rack in the middle of the oven and heat to 400°F. Generously coat a 12-cup standard muffin tin with cooking spray or olive oil.
Place the sausage in a medium skillet over medium-high heat and cook, breaking the meat into small pieces with a wooden spoon, until browned and cooked through, 7 to 8 minutes. Evenly divide 3/4 of the sausage between the muffin wells.
Divide the mushrooms, onion, and spinach evenly between the muffin wells. Top with the remaining sausage. Place the eggs, ghee, salt, and pepper in a medium bowl and whisk until the eggs are completely incorporated. Pour into the muffin wells, filling each 1/2 to 3/4 full.
Bake until the eggs are set and lightly browned around the edges, 12 to 14 minutes. Place the pan on a wire rack and let cool for 2 to 3 minutes. Run a butter knife around each cup to the loosen the muffins before removing them from the pan. Serve warm or cool completely on a wire rack before refrigerating or freezing