Step 1Combine tahini, chicken broth, lemon juice, cumin and paprika, stirring well.
Step 1Dip the bread in cold water and squeeze dry against the bottom of a fine sieve. In a large bowl, mix bread with beef, lamb, onion, salt, cumin, allspice, red pepper and black pepper. Mix thoroughly, but avoid overhandling. Refrigerate for 1 hour.
Step 2Mix in parsley, mint and walnuts with your hands and shape mixture into balls.
Step 3Heat 1 tablespoon oil over medium heat in a large skillet. Add half the meatballs and saute until browned and cooked through, about 7 minutes. Regulate heat so meatballs don't burn, and shake pan vigorously to turn them. Transfer to paper towels. Wipe skillet and repeat with remaining oil and meatballs.
Step 4Top with onions. Garnish and serve hot or warm, with tahini sauce.