Aharmonious medley of fillings -- thin slices of serrano ham, goat cheese, asparagusspears, and chopped mint -- is folded into a fluffy baked omelet,which will be cut into wedges to serve.
Preheat oven to 375 degrees. Prepare an ice-water bath; set aside. Bring a wide medium saucepan of water to a boil. Add the asparagus, and cook until bright green and just tender, 2 to 3 minutes. Plunge asparagus into ice-water bath to stop the cooking; let cool completely. Drain; halve lengthwise, and set aside.
Melt butter in a 12-inch ovenproof nonstick skillet over medium heat. Remove skillet from heat; set aside. Whisk together egg yolks, flour, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a medium bowl until pale and thick; set aside.
Put egg whites and a pinch of salt into the bowl of an electric mixer fitted with the whisk attachment. Beat on medium-high speed until stiff peaks form. Fold whites into yolk mixture. Using a large rubber spatula, spread mixture evenly into reserved skillet. Bake until omelet is almost set but still soft, about 6 minutes.
Sprinkle goat cheese and mint over half the omelet. Top with asparagus and a layer of ham. Fold plain half over filled half. Bake until cheese has melted and omelet is cooked through, about 3 minutes. Cut into 4 wedges, and serve.