Bring a large pot of water to a boil. Season with salt; add pasta and cook, stirring occasionally, until 1 minute before al dente, about 2 minutes for fresh pasta, longer for dried. Drain, reserving 1/4 cup pasta water.
Meanwhile, melt butter in a large heavy nonstick skillet over medium-high heat.
Saute chicken 2-3 minutes, turn and add prosciutto; sauté until browned, about 3 more minutes.
Add reserved pasta water, orange juice, half of zest, and cream; bring to a boil.
Add pasta; cook, stirring, until sauce coats pasta and pasta is al dente, about 1 minute.
Season with salt and pepper.
Stir in cheese and divide among warm bowls.
Makes 2 really big servings or 4 regular servings