1. In a large skillet cook sausage, onion, sweet pepper, and garlic until sausage is brown, stirring often. Drain off fat. Set sausage mixture aside to let cool.
2. In a large bowl stir together cream cheese, Parmesan cheese, milk, mayonnaise, and sour cream. Add sausage mixture, spinach, and banana peppers; gently stir to combine. Spread mixture into a 9-inch fluted quiche dish or deep-dish pie plate.
3. Bake in a 350 degree F oven about 30 minutes or until bubbly. Serve with crostini, bagel chips, blue corn tortilla chips, or French bread.
4. Makes 5 cups dip
5. To make ahead: Prepare as directed through Step 2. Cover and chill for up to 24 hours. Uncover and bake about 40 minutes or until heated through.