Preheat the oven to 90°C (to keep cooked waffles warm).
Combine the oil, coriander, flour, parsley, baking powder, cumin, salt, coriander, cayenne, egg whites, garlic and chickpeas in a food processor and pulse until smooth.
Lightly brush the top and bottom of the waffle iron with oil. Fill the waffle iron about three-quarters of the way full (some waffle iron should still be showing). Close the lid gently and cook until the falafel is golden brown and firm in the center, 6 to 10 minutes. Keep the cooked falafels warm in the oven or covered with foil on a plate while you make the remaining falafels.
To build the sandwiches, stuff each pita half with a falafel. Add your choice of toppings, drizzle with the hummus and sprinkle with a few dashes of hot sauce.
Cook's Note: The falafels can be frozen in resealable plastic bags for up to 1 month. Reheat in a toaster oven or 150°C oven until warmed through and crisp.
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