While the water comes to a boil, start the sauce: Heat the oil in a 12-inch skillet over medium heat. Add the sausage and cook until it begins to brown, about 7 minutes. Remove and set aside.
Add 2 tablespoons of the salt and bring back to a rolling boil. Add the pasta and cook until al dente according to package directions.
While the pasta cooks finish your sauce. Add the mushrooms to the skillet and cook until they begin to deeply brown, about 8 minutes, adding more oil if needed.
About 1 minute before the pasta is finished cooking add the asparagus to the pasta pot. Reserving 1 cup of the pasta water, drain the pasta and asparagus and add to the skillet with the mushrooms and toss together. Add back the reserved sausage and toss together again, adding in pasta water, as needed to loosen up the sauce.
Plate in bowls and garnish with chives. Season with flaky slate and pepper, if desired.