Preheat the oven to 375 degrees F. Combine the eggs, milk, green onion, salt and pepper in a small bowl. Place the tart shells on a large baking sheet. Divide and place half the cheese in the bottom of each tart shell. Divide and set the shrimp on top of the cheese. Pour the egg mixture into the tarts. Top each tart with an equal amount of the remaining cheese. Bake for 20 to 25 minutes, or until lightly puffed and golden brown.