In medium saucepan, cook fettucine noodles as directed on package. Drain.
In skillet, prepare homemade white sauce. Melt butter and whisk in flour until turns into paste. Whisk in milk and whisk vigorously, until paste dissolves into milk. Whisk for 2-3 minutes, or until sauce begins to thicken. Add 1/4 - 1/2 cup parmesan cheese and whisk until melts into the sauce. Add 1 Tbsp at a time of milk for a thinner sauce or 1 Tbsp at a time of flour for a thicker sauce. Once sauce has thickened, add chicken pieces and cover and cook for 8-10 minutes, or until chicken is no longer pink. Stir frequently.
Cook frozen peas according to package directions.
Toss cooked fettucini and peas into the skillet with the chicken and white sauce. Stir through.
Slit or vent sweet potatoes. Add sweet potatoes to baking dish with inch of water and cover with foil. Bake sweet potatoes at 350 for 1 hour. Remove and let cool about 10 minutes. Peel skins off of the sweet potato and mash.
Serve Fettucine Alfredo with Mashed Sweet Potatoes.