Wash the meat and dab dry. Heat the oil in a pan and fry the meat in it over medium heat for about 5 minutes on each side. Season with salt, pepper and paprika. Cook pasta in boiling salted water for about 9 minutes.
Clean the carrot, peel it and cut it lengthwise into thin strips. Add to the spaghetti about 5 minutes before the end of the cooking time and cook with it. Bring stock and lemon juice to the boil in a pot. Add sauce thickener while stirring and bring to the boil again.
Stir in sour cream. Pluck basil leaves from the stalk and cut into strips. Add to the sauce and season with salt and pepper. Drain spaghetti and carrots and arrange on a plate with the sauce.
Cut the chicken filet into slices and lay it on the spaghetti-carrot bed. Sprinkle with pepper and serve garnished as desired with basil and a lemon wedge.