1. Bring a large pot of lightly salted water to boil over high heat. Cook pasta following package directions, 11 to 12 minutes. Add peas during last 1 minute of cook time. Drain and return to pasta pot.
2. Meanwhile, prepare sauce. Melt butter in medium-size saucepan over medium heat. Whisk in flour, then slowly whisk in fat-free half-and-half. Season with 1/2 teaspoon of the salt and 1/8 teaspoon of the nutmeg. Bring just to boiling, stirring frequently, 8 minutes.
3. While the sauce cooks, season sirloin with remaining 1/4 teaspoon salt, 1/8 teaspoon nutmeg and 1/4 teaspoon pepper. Heat oil in a large nonstick skillet over medium-high heat. Add steak and cook 3 minutes.
4. Remove sauce from heat; whisk in Parmesan. Turn steak and cook another 3 minutes or until desired doneness. Pour sauce over pasta; toss to combine. Transfer to a platter. Slice steak; fan over fettuccine.