Step 1

Combine lamb, salt, pepper, and oregano in medium bowl. Mix with hands until homogeneous. Cover and refrigerate at least 1 hour or up to over night. Meanwhile, place yogurt in fine-mesh strainer set over small bowl. Allow to drain in refrigerator for 1 hour. Adjust oven rack to middle position and preheat oven to 300°F. Place cold mixture in bowl of food processor with onion, garlic, and bacon. Process until smooth puree is formed, about 1 minute total, scraping down sides with rubber spatula as necessary.

Step 2

Line rimmed baking sheet with aluminum foil. With moist hands, form meat mixture into rectangle about 1 1/2 inches high, 8-inches long, and 5-inches wide. Bake until center of loaf reads 155°F on an instant read thermometer, about 30 minutes. Allow loaf to rest at room temperature for fifteen minutes (or refrigerate for up to a week—see note)

Step 3

Meanwhile, make sauce. Combine strained yogurt, mayonnaise, garlic, lemon juice, and parsley and stir to combine. Season to taste with salt. Refrigerate, covered, until ready to use.

Step 4

Adjust broiler rack to highest position (about 1 1/2 to 2 inches from broiler element) and preheat broiler. Slice loaf crosswise into 1/8th to 1/4-inch strips (each strip should be about 5-inches long and 1 1/2 inches wide). Lay strips on rimmed baking sheet lined with aluminum foil and broil until edges are brown and crispy, about 2 minutes. Tent with aluminum foil. Warm bread by placing on rimmed baking sheet and broiling until soft and pliant, about 45 seconds per side.

Step 5

Spread 1/4 cup of sauce over each piece of bread. Divide meat evenly between sandwiches. Top as desired, wrap with foil, and serve.