Greek-Style Lamb Pita Sandwiches

1. FOR THE LAMB PATTIES: Adjust oven rack to middle position and heat oven to 350 degrees. Cut top quarter off each pita bread. Tear quarters into 1-inch pieces. (You should have 3⁄4 cup pita pieces.) Stack pitas and tightly wrap with aluminum foil. Process pita bread pieces, onion, oregano, lemon juice, garlic, salt, and pepper in food processor until smooth paste forms, about 30 seconds. Transfer bread mixture to large bowl; add lamb and gently mix with hands until thoroughly combined. Divide mixture into 12 equal pieces and roll into balls. Gently flatten balls into round disks about 1⁄2 inch thick and 2-1⁄2 inches in diameter. (Patties can be prepared through step 1 and refrigerated for up to 1 day or frozen before cooking as directed in step 2. Frozen patties should be thawed in refrigerator prior to cooking.)
2. Place foil-wrapped pitas directly on oven rack and heat for 10 minutes. Meanwhile, heat oil in 12-inch nonstick skillet over medium-high heat until just smoking. Add patties and cook until well browned and crust forms, 3 to 4 minutes. Flip patties, reduce heat to medium, and cook until well browned and crust forms on second side, about 5 minutes longer. Transfer patties to paper towel–lined plate.
3. Using soupspoon, spread 1⁄4 cup Tzatziki Sauce inside each pita. Divide patties evenly among pitas; fill each sandwich with tomato slices, 1⁄2 cup shredded lettuce, and 2 tablespoons feta. Serve immediately.

GREEK-STYLE LAMB PITA SANDWICHES WITH BEEF
Decrease lemon juice to 1 tablespoon, increase oregano to 2 tablespoons, increase garlic to 3 cloves, and increase oil to 1 tablespoon. Substitute 1 pound 80 percent lean ground chuck for lamb.

GRILLED GREEK-STYLE LAMB PITA SANDWICHES
The grill imparts a smoky flavor to the meat and pitas in this variation.
1A. FOR A CHARCOAL GRILL: Open bottom vent completely. Light large chimney starter filled three-quarters full with charcoal (4-1⁄2 quarts). When top coals are partially covered with ash, pour evenly over half of grill. Set cooking grate in place and cover. Heat grill until hot, about 5 minutes.
1B. FOR A GAS GRILL: Turn all burners to high, cover, and heat grill until hot, about 15 minutes. Leave primary burner on high and reduce other burner(s) to medium-high.
2. Clean and oil cooking grate. Place patties on hotter side of grill, cover (if using gas), and cook, turning once, until well browned and crust forms on each side, 8 to 12 minutes. Transfer patties to plate. Place pitas in single layer on hotter side of grill. Cook, turning once, until each pita is thoroughly warmed and faint grill marks appear, 30 to 40 seconds. Remove pitas from grill and wrap tightly with aluminum foil until ready to assemble sandwiches.