Cook pasta according to package directions, omitting salt and fat. Drain pasta in a colander over a bowl, reserving 1/2 cup cooking liquid.
While pasta cooks, heat oil in a large nonstick skillet over medium-high heat. Add garlic; sauté 15 seconds. Add prosciutto and spinach; sauté over medium-high heat 3 minutes or until wilted.
Combine reserved 1/2 cup cooking liquid and egg in a bowl; stir well with a whisk. Add pasta and egg mixture to pan; stir well. Cook over low heat 4 minutes or until egg mixture is slightly thick, stirring constantly (do not boil). Stir in 1/4 cup cheese and pepper. Spoon 1 cup pasta mixture onto each of 4 plates; top each serving with 1 tablespoon cheese. Serve immediately.