Cook fettucini according to package. While cooking... Melt butter, stir in flour. I prefer to use a whisk to stir so that there are no "lumps". Gradually add half and half, stir until thickened. Add Parmesan; cook and stir until smooth. Fold in seafood, heat 3 mintues, stirring occasionally. Toss fettucini with sauce, sprinkle with parsley. Serve immediately.