PreparationFor the sauce: In a small bow, whisk the yogurt with the lemon juice. Stir in the chopped herbs, season with salt and refrigerate until ready to use. For the patties and pita: In a bowl, use your hands to mix together all of the ingredients, except for the pita. Form the mixture into twelve 3-inch oval patties (about 1 inch thick). Arrange the patties on a plate and refrigerate for at least 30 minutes, until firm Preheat a grill for at least 10 minutes and prepare it for grilling over moderately high heat. If you are using a charcoal grill, leave one area where you can grill the pita indirectly. Oil the grill grates and grill the patties until dark brown grill marks form on the bottom, 5 to 6 minutes. Flip the patties and grill for 4 to 6 minutes longer, until just cooked through. Meanwhile, wrap the pita in foil and set the package on the top shelf of a gas grill or in the cooler spot of a charcoal grill and allow them to warm through, 8 to 10 minutes. Wrap 2 or 3 patties in each pita, spoon some of the yogurt sauce alongside and serve with herb sprigs, passing the remaining yogurt sauce at the table.