Bring 3 quarts of water to a boil and add 1 tablespoon of salt. Set up an ice bath nearby. Cook the asparagus spears in the boiling water until very tender, about 3 minutes. Drain and immediately plunge in the ice bath. Once the asparagus spears are cooled, drain and pat dry. Slice each spear very thinly on the diagonal, reserving ¼ cup for garnish.
In a medium bowl, combine the asparagus, ricotta, Parmigiano-Reggiano, olive oil, salt and pepper and stir well to combine.
Roll out the pasta dough to the thinnest setting on a pasta machine. Cut the pasta sheets into 4-inch rectangles. Place a scant tablespoon of the ricotta filling on one half of each rectangle, then fold them over like a book to enclose the filling. Press the edges of each ravioli with your fingers to seal. The ravioli can now be frozen between sheets of parchment until ready to cook.
Bring 6 quarts of water to a boil and add 2 tablespoons of salt.
In a 14- to 16-inch sauté pan, heat the butter over high heat until the foam subsides. Add the reserved asparagus and remove from the heat. Cook the ravioli in the boiling water until they are tender and cooked through (you should taste one to test it), about 3 minutes. Drain the ravioli and add them to the pan with the butter. Add 3 tablespoons of the pasta cooking water and toss gently over high heat for 1 minute. Season with salt and pepper. Divide evenly among 8 warmed pasta bowls and serve immediately with Parmigiano-Reggiano grated over the top.