Preheat the broiler.
In a mixing bowl whisk together the eggs and water. Add potatoes, red pepper, zucchini, mushrooms, garlic, salt and pepper. Fold in 1/4 cup Asiago cheese. Set aside.
In a large nonstick skillet, melt the butter over medium heat. Add the shallots and saute for 4 minutes. Stir in the egg mixture. Cover, reduce the heat to low and cook until the eggs are almost set, about 10 minutes.
Sprinkle the frittata with the remaining Asiago. Place the frittata under the broiler and cook until the top is set and starts to brown, about 3 minutes. Place a large serving plate over the pan, and carefully invert to turn out the frittata to serve.
Yield: 4 servings