Preheat oven to 350°F. Spray 2, 10-ounce soufflé dishes or custard cups with non-stick spray. Cook asparagus in large pot of boiling water until crisp-tender, about 2 minutes. Drain. Cool in a large bowl of ice water. Drain. Pat dry with paper towels. Cut crosswise into 1/8-inch-thick slices.Whisk the whole eggs, chives, lemon peel, tarragon, salt, and pepper in medium bowl until blended and frothy. Stir in asparagus. Stir in 1/4 cup ricotta, allowing some clumps to remain. Using an electric mixer, beat the egg whites in another medium bowl until firm peaks form. Fold egg whites into asparagus mixture just until blended. Divide egg mixture among prepared soufflé dishes, spooning 1 tablespoon of ricotta atop each. Bakeuntil frittatas are just set and tops begin to brown, about 15 minutes. Serve warm.
