In small saucepan, bring couscous and water to a boil; turn off heat, cover and let stand until liquid is absorbed and couscous is tender, about 10 minutes- Reserve 1 cup couscous and save remaining for another use.
Meanwhile, steam broccoli until tender, 5 to 7 minutes- Remove from steamer and set aside to cool.
In medium skillet, heat oil over medium heat. Add onion and cook, stirring often, until soft, about 5 minutes- Stir in cumin.
Remove from heat and allow to cool.
Preheat oven to 400 degrees, then line a large cookie sheet with foil, and dust with breadcrumbs.
In food processor, combine couscous, broccoli, onions, chickpeas and tahini- Process until blended, stopping to scrape down sides of bowl when necessary.
Transfer mixture to large bowl.
Gradually add 1/4 cup bread crumbs- Add enough additional bread crumbs until mixture is stiff enough to form into patties but still moist- Season with salt.
Shape mixture into 3-inch patties (1/2-inch thick).
Put patties on prepared cookie sheet- Bake until lightly browned on both sides about 50 minutes, turning once halfway.
They can be served at this point or grilled or broiled until crispy for 1 or 2 minutes per side.