Divide meat into 8 equal parts. Flatten 4 portions into 4-inch patties. Place one-fourth (about 2 tablespoons) of one of the fillings in the center of each patty, spreading to within 1/2 inch of the edges.

Flatten the remaining 4 meat portions into 4-inch patties and gently place each on top of the filled patty, pressing the edges together to seal. Sprinkle garlic salt and pepper on each burger. For a charcoal grill, grill burgers on the rack of an uncovered grill directly over medium coals for 14 to 18 minutes or until an instant read thermometer inserted near the center registers 160 degree F, turning once. (For a gas grill, preheat grill. Reduce heat to medium. Place burgers on grill rack over heat. Cover and grill as above.) Remove burgers from grill. Makes 4 burgers.

In a small bowl, mix 2 tablespoons finely chopped tomato, 2 tablespoons finely chopped, seeded fresh jalapeno chili pepper, 2 tablespoons snipped fresh cilantro, and 2 tablespoons thinly sliced green onion.

In a small bowl, combine 1/4 cup seeded and finely chopped tomato, 1 ounce crumbled feta cheese, 2 teaspoons finely chopped red onion, 2 teaspoons finely chopped pitted ripe olives, 1/4 teaspoon red wine vinegar, 1/4 teaspoon olive oil, and 1/8 teaspoon dried oregano, crushed. Cover and chill in refrigerator for at least 30 minutes before using.

In a small bowl, combine 1/4 cup mayonnaise, 1/4 cup grated Parmesan, 2 tablespoons finely chopped green onion, and 2 tablespoons finely chopped pitted ripe olives.