Preheat the oven to 350°F (175°C) and spray a muffin tin with cooking spray.
Cook the sausage in a skillet over medium heat until browned and crumbled. Drain excess fat.
In a mixing bowl, whisk together eggs, heavy whipping cream, salt, and pepper.
Stir in the cooked sausage, shredded Cheddar, shredded Swiss cheese, and green onions (optional).
Spoon the mixture into the prepared muffin tin, dividing it evenly.
Sprinkle any remaining cheese on top.
Bake for 20-25 minutes, or until the quiches are set and golden brown.
Let them cool for a few minutes before serving.