Cut chicken breasts into strips and fry each side in 1 tablespoon hot oil for 3-4 minutes. Season with salt and pepper and keep warm. Trim mushrooms and cut into slices.
Rinse bell peppers, trim, cut in half, remove seeds and cut into fine strips. Saute in remaining oil for a few minutes and season with salt and pepper.
Rinse tomatoes, slice into quarters, remove seeds and dice. Add mushrooms to bell peppers, cook briefly and season with paprika, salt and pepper. Warm tortillas in the oven and cover with chicken strips, vegetables and lettuce leaves and roll up firmly. Serve on lettuce leaves if desired.