Cook the spaghetti in plenty of boiling salted water for about 10 minutes. Drain and let drain. In the meantime peel and chop the onion. Clean the mushrooms and halve or quarter them depending on size. Clean and wash the bell peppers and cut them into fine strips.
Cut out 8 butterflies from turkey breast slices, cut the rest of the meat into strips. Wash sage, dab dry and cut leaves into strips. Heat oil in a frying pan. Fry onion and mushrooms for about 4 minutes. Add bell peppers and turkey strips, fry for about 3 minutes. Dust with flour, stir in and deglaze with stock and cream. Stir in sage and season with salt and pepper. Bring sauce to the boil and mix with the noodles. Put on plates.
Add bell peppers and turkey strips, fry for about 3 minutes. Dust with flour, stir in and deglaze with stock and cream. Stir in sage and season with salt and pepper. Bring sauce to the boil and mix with the noodles. Put on plates. Garnish with the "butterflies" and sage as desired