Start with the lamb sauce:

1. Place a large skillet over medium heat and add olive oil. Once hot add the onion, carrot, celery and garlic and cook for 4 minutes over medium heat
2. Stir in vinegar and caramelize for 1 to 2 minutes
3. Add in the lamb and mince and brown with the veggies
4. Next add in the sumac and stir into the meat then fully cook the lamb
5. Add in the wine, tomatoes, tomato paste and broth and stir
6. Bring to a low boil then cook for about 20 minutes or until the sauce as a thicker consistency (similar to bolognese)

While the sauce cooks:

1. Warm the butter and melt in a sauce pan
2. Add in the flour and whisk over medium heat
3. Add in the milk and continuously whisk until sauce thickens and remove from heat

Assemble lasagna:

1. Preheat oven to 400 degrees F
2. Grease a 9×13 or similar size baking dish with oil then add spoonful of the béchamel sauce and spread across the dish
3. Place 3 lasagna sheets over it followed by a generous spoonful of the lamb sauce
4. Sprinkle a third of the feta cheese across then repeat with remaining layers (about 3 times)
5. Drizzle with olive oil then cover lasagna with foil then bake for about 40 to 45 minutes or until cheese is melted and the noodles are softened and cooked. I like to remove foil for last 5 minutes and broil if desired for about 1 minute on low for cheese to bubble
6. Garnish with dried oregano and serve!