Spaghetti with asparagus, shitake mushrooms, lemons and chives

This is one of Kristin's favorite recipes. She sent it to Tim and I to try. We followed the recipe exactly as stated make no substitutions. This is a great recipe. Very favorable. A must recipe to try especially when asparagus is in season.

Ingredients:

12 ounces spaghetti
4 T butter divided
2 T extra virgin olive oil
1/2 C thinly sliced shallots (about 4)
1 pound fresh shiitake mushrooms, stemmed, sliced
6 T fresh lemon juice (do not substitute)
1 3/4 C vegetable broth
1 T grated lemon peel
1 pound asparagus, tough ends trimmed, cut crosswise in thirds
1/4 C chopped fresh chives
4 ounces shaved Asiago cheese

Preparation:
Cook spaghetti in large pot of boiling water until tender but still firm to bite, stirring occasionally. Drain. Transfer pasta to large wide bowl.

Meanwhile, melt 2 tablespoon butter with oil in heavy large skillet over medium heat. Add shallots;saute 1 minute. Add shiitake mushrooms; sprinkle with salt and pepper. Saute shiitake mixture until soft, about 6 minutes. Add lemon juice;cook 1 minute. Add broth and lemon peel. Bring to boil, then reduce to medium and simmer until liquid is reduced by half, about 6 minutes. Add asparagus to mushroom mixture;simmer until asparagus turns green, about 2 minutes. Add chives and remaining 2 tablespoons butter and stir until butter melts. Season sauce to taste with salt and pepper.

Pour sauce over pasta; toss to coat. Top with shaved asiago and serve.