Process mushrooms in food processor until coarsely chopped, about 10 pulses, scraping down sides of bowl as needed. Transfer mushrooms to bowl; set aside.

In now-empty processor, pulse bread, milk, ½ teaspoon salt, and ½ teaspoon pepper until paste forms, about 8 pulses. Add turkey and pulse until well combined, about 6 pulses.

Heat oil in 12-inch skillet over medium heat until shimmering. Add onion, mushrooms, ½ teaspoon salt, and ¼ teaspoon pepper and cook until liquid has evaporated, 8 to 10 minutes.

Stir in tomato paste, garlic, oregano, and cinnamon and cook until fragrant and tomato paste turns rust colored, about 1 minute. Stir in tomato sauce.

Add turkey mixture and cook, breaking into small pieces with spoon, until no longer pink, about 6 minutes. Remove from heat and set aside.

Adjust oven rack to middle position and heat oven to 375 degrees.

Bring 2 quarts water to boil in Dutch oven. Add macaroni and ½ tablespoon salt and cook until al dente. Drain in colander, rinse with cold water until cool, and then drain again thoroughly. Transfer macaroni to large bowl.

Whisk cornstarch together with ½ cup low-fat milk and set aside.

Combine oil and garlic in now-empty pot and set over medium-high heat. Once garlic begins to brown, add evaporated milk and remaining 2 ½ cups low-fat milk and bring to boil, stirring occasionally to prevent scorching.

Whisk cornstarch mixture to recombine, then whisk into pot. Return to boil, whisking constantly, and cook until thickened, about 1 minute.

Off heat, whisk in 1 cup Pecorino. Season béchamel with salt and pepper to taste.

Grease 13 by 9-inch baking dish with vegetable oil spray. Stir 2 cups béchamel into macaroni until combined.

Transfer sauced macaroni to prepared dish. Spread meat sauce over macaroni.

Whisk yogurt into remaining béchamel, then pour over meat sauce. Sprinkle pastitsio with remaining ¼ cup Pecorino.

Bake until golden brown, 30 to 35 minutes, rotating dish halfway through baking. Let cool for 20 minutes. Serve.