Heat a large frying pan on high. Cook sausages for 5 minutes, until browned. Remove from pan and set aside.
Heat oil in pan on medium. Cook leek and garlic, stirring, for 5 minutes, until soft. Return sausages to pan with chicken stock and capsicum and bring to boil. Reduce heat to low and simmer for 2 minutes, until sausage is cooked. Remove from heat.
Meanwhile, cook farfalle in a large saucepan of boiling, salted water according to packet directions. Drain and return to saucepan. Add sausage mixture and fold through spinach, basil and half of parmesan. Cover and stand for 3 minutes, until spinach wilts. Serve sprinkled with remaining parmesan.