Bring a large pot of salted water to a boil. Add the penne and cook, stirring occasionally, until al dente. Drain.
Meanwhile, in a large skillet, heat the olive oil. Add the garlic and asparagus and cook over moderately low heat, stirring occasionally, until the garlic is fragrant, about 3 minutes. Add the stock and boil over high heat until reduced by half and the asparagus are tender, about 5 minutes.
Add the peas and cream to the skillet and boil over high heat until the sauce has thickened, 3 minutes. Stir in the penne and cook until heated through. Remove from the heat and stir in the butter, sage and the 1/2 cup of cheese. Season with salt and pepper. Transfer the pasta to bowls and serve right away, passing additional cheese at the table.