As an alternative to the squash, heat 1 tbsp olive oil in a frying pan and fry 500 g/1 lb 2 oz skinless, boneless chicken breasts, cut into pieces, for 5 minutes until browned all over. Remove the chicken from the pan with a slotted spoon and finely chop. Add 1 finely chopped leek and 2 tbsp chopped sage to the pan, adding a little extra oil, if needed. Cook the leek for 5 minutes until softened, then return the chicken to the pan, remove from the heat and stir until combined.
Fill the part-cooked pasta shells with the chicken mixture, cover with the Tallegio sauce and bake as described on the previous page.