Cook pasta in large pot of rapidly boiling salted water until al dente. Drain well.
In a large pan, heat the oil. Add the leek and bell pepper and stir-fry over medium heat for 2-3 minutes. Add spinach and mushrooms and toss together for about 1 minute, or until spinach just begins to wilt. Set aside.
Make the dressing: mix garlic, cumin, coriander, and vinegar together in a bowl. Gardually whisk in the olive oil.
In a salad bowl, toss the pasta, vegetables, beans, chives, and black pepper. Add the dressing and toss. Sprinkle sunflower seeds over the top and serve.