Preheat oven to 400 degrees.
Melt the butter in a large skillet set over medium heat and lightly sauté the shallot, onions, snap peas, asparagus and spinach until the spinach is limp, about 1 minute, then cover and continue cooking until the asparagus is just tender, another minute or so.
In a large bowl, beat the eggs and then beat in the parsley and thyme, with a little salt and pepper. Pour egg mixture over the vegetables in the skillet and cook over medium-low heat until the bottom of the frittata is firm, about 10 minutes. Sprinkle the cheese on top and transfer the skillet to the oven. Bake, checking every 5 minutes or so, until the top of the frittata is no longer runny and the cheese is melted and bubbly, about 10 to 20 minutes more.
Nutrition information per serving:
Calories285Fat20 gSodium222 mg
Carbohydrates8 gSaturated fat9 gCalcium137 mg