Cook the pasta in boiling salted water according to the instructions on the packet, drain and allow to drain. Clean, wash and cut leek into rings. Cut ham sausage diagonally into thin slices. Put kidney beans in a sieve and drain. Heat oil in a pan and fry the sausage lightly in it. Add the leek and fry for another 3 minutes. Add kidney beans and noodles and fry for about 4 minutes.
In the meantime melt fat and stir in flour. Add stock and milk slowly while stirring and bring sauce to the boil. Remove the pasta pan from the heat and keep warm. Add processed cheese to the sauce, season with salt and pepper and bring to the boil again. Wash parsley, dab dry and put 1 leaf aside for garnishing. Cut remaining leaves into strips and put them into the pan. Finally pour the sauce over the noodles and garnish with parsley.