In a large pot boil 4 cups water with salt. When boiling, add asparagus and cook 3-5 minutes, until tender crisp.
Remove with a slotted spoon and drain asparagus in colander.
Add the pasta then cook according to package directions for al dente. Reserve 1 cup pasta water before draining.
Meanwhile, in a large sauté pan heat olive oil. Add garlic and cook until golden, add asparagus, salt and pepper and sauté about 1-2 minutes, tossing with oil and garlic.
In a small bowl combine egg yolk, Parmigiano-Reggiano cheese, ¼ cup reserved pasta water, salt and pepper. Mix well.
After pasta is drained return to pot and mix with egg mixture. Cook on medium-low about 2 minutes, until sauce thickens and sticks to pasta.
Toss in asparagus and mix well. Adjust salt and pepper to taste.
If pasta seems too dry add more reserved liquid a tablespoon at a time.
Serve with additional grated cheese.
