For the right consistency, use a thick Greek yogurt. You can prepare (but not cook) the burgers up to a day ahead, then cover and refrigerate until you’re ready to use.

Ingredients
1/2 cup rinsed quinoa
1 medium carrot, cut in large chunks
6 scallions, thinly sliced
15 ounces great northern beans, drained and rinsed
1/4 cup plain dried breadcrumbs
1 large egg, lightly beaten
1 tablespoon ground cumin
Coarse salt
Ground pepper
2 tablespoons olive oil
1/2 cup plain nonfat Greek yogurt
1 tablespoon fresh lemmon juice
4 pita breads (6 inch)
1/2 English cucumber, thinly sliced diagonally
 
Directions
1. In a small sausepan, bring 3/4 cup of water to a boil; add quiona, cover, and reduce heat to low. Cook until liquid is absorbed, 12 to 14 minutes; set aside.

2. In a food processor, pulse carrot until finely chopped. Add cooked quinoa, half the scallions, beans, breadcrumbs, egg, cumin, 1 teaspoon salt, and 1/4 teaspoon pepper; pulse until combined but still slightly chunky.

3. Form mixture into four 3/4-inch-thick paties (dip hands in water to prevent sticking). If too soft, refrigerate 10 minutes to firm. In a large nonstick skillet, heat oil over medium; cook burgers until browned and cooked trhough, 8 to 10 minutes per side.

4. Meanwhile, in a small bowl, combine yogurt, lemon juice, and the remaining scallions; season with salt and pepper. Serve burgers in pita topped with cucumber and yogurt sauce. Serves 4.

Source:  www.marthastewart.com