For the garnish:
In a small bowl, mix the sour cream with the lemon zest and juice; set aside.
For the filling:
In a small sauté pan, heat the butter over medium heat. Add the shallot and salt; sauté about 1 minute. Reduce the heat to low, add the asparagus, and sauté until tender and a bit browned, about 4 minutes. Take the pan off the heat and stir in the prosciutto; set aside.
For the omelet:
In a medium bowl, whisk together the eggs, water, salt, pepper, and mint until the yolks and whites are well combined but not foamy. In an 8-inch heavy-duty nonstick skillet over medium-high heat, heat the oil and then add the butter. Swirl to coat the pan.
When the butter melts, pour the eggs into the pan. With a heatproof spatula, scramble the eggs using small, circular scribbling motions until soft curds start to form, 30 to 50 seconds.
As the mixture firms, spread it over the bottom of the pan; swipe the sides as needed. Stop working the curds to let the omelet begin to firm and let it sit about 30 seconds. (If you like your eggs well done, let it go a bit longer.)
Scatter the Asiago evenly, leaving a scant margin around the omelet’s edge. Add the asparagus-prosciutto mixture and use your spatula to gently press them into the curds to incorporate the filling into the omelet.
With the spatula, lift one-third of the omelet and fold it over the center like a business letter.
Tilt the pan toward the plate to slide the omelet so one-third of it hangs over the pan’s edge. Invert the pan, using the spatula to help support the omelet so that it flips neatly over itself as it slides out of the pan.
Garnish with the sour cream and the remaining mint.
nutrition information (per serving):
sat fat g
Photo: Scott Phillips