In a non-stick ovenproof skillet, soften the onion, garlic and pine nuts in the oil for about 4 minutes. Pour the egg mixture into the skillet and stir gently with a spatula for 30 seconds. Sprinkle with the basil and cheese. Bake for 7 to 10 minutes or until the eggs are set and begin to puff. Finish cooking under the broiler until the frittata is golden brown.