Preheat oven to 400 degrees F. LIghtly coat a springform pan or a 9 inch cake pan.
Heal your olive oil in a large skillet over medium high heat. One at a time, add a tortilla and cook until crisp and lightly browned, about 1-2 minutes per side.
Place 1 tortilla on the bottom of the springform pan. Spread 2-3 tablespoons sour cream evenly over the top, followed by chicken, sharp cheddar, pepper jack and mozzarella. Repeat with 3 more layers. Top with remaining tortilla, sour cream and cheeses.
Bake for 25-30 minutes, or until the cheeses have melted and the stack is heated through.
Cut into slices and garnish with avocado and tomato, if desired.