In a large skillet, cook the sausage over medium heat until meat is no longer pink.
Add garlic; cook 1 minute longer. Drain.
Stir in 2 cups cheese. Transfer to a greased 9-inch deep-dish pie plate.
In a small bowl, combine the milk, eggs, biscuit mix, sage and pepper. Pour over sausage mixture.
Bake at 400°F for 20-25 minutes or until a knife inserted near the center comes out clean.
Sprinkle with remaining cheese; bake 1-2 minutes longer or until cheese is melted.
Let stand for 10 minutes before cutting.
