Cook the orzo in salted,
boiling water until tender, about 12 minutes.
In a large bowl, lightly
beat the eggs. Stir in the milk, salt, pepper and orzo.
Melt the butter in a
large nonstick ovenproof skillet. Over medium heat, sauté the leeks
and squash for 5 minutes, stirring occasionally. Do not overcook; the vegetables
will be baked later.
Increase the heat to
high. When the mixture is almost smoking, stir in the basil and pour in the
egg mixture. In about 45 seconds the mixture will start to bubble around the
edges. Remove the skillet from the burner and place in the center of the oven.
Bake until the frittata
is set, about 30 minutes. Shake the pan to loosen the sides, then flip the
frittata over onto a large ovenproof serving dish.
Preheat the broiler.
Sprinkle the frittata with Gruyère cheese and place it under the broiler
20 seconds. Let cool at least 5 minutes before cutting into wedges. Serve
immediately.