Cook butternut/pumpkin pieces in boiling water until soft.
Meanwhile, heat cooking oil in a skillet over high heat. Season chicken with salt and black pepper. Cook until lightly browned while stirring. Transfer to a bowl or plate.
In the same pan saute onion and garlic over medium heat until onions are soft.
Add leek and cook until soft. This will take 5-10 min.
Puree pumpkin, add water if needed.
Combine pumpkin puree, leek mixture, drained pasta, and chicken. Season with salt and pepper to taste. Cook until heated through.