For the grape leaves: Mix the ground lamb, rice, mint, cumin, allspice, cinnamon, cayenne, 1 1/2 teaspoon salt and 1/2 teaspoon freshly ground pepper.
Unroll the grape leaves, cutting off any stem, and pat dry. Add 1 1/2 tablespoons of filling and roll up, tucking in the sides. Be careful not to overstuff.
Layer the leftover grape leaves in the bottom of the pot. Season the lamb chop with salt and pepper and place over the loose grape leaves. Line the rolled grape leaves on top of the lamb chop. Drizzle with the juice of 2 lemons. Fill the saucepan with water, only covering the rolled grape leaves. Place a plate over the top of the grape leaves to prevent them from unfolding. Cover and bring to a boil, then reduce the heat and simmer for about 30 minutes.
For the sauce: You are making a bechamel sauce. Melt the butter, then add the flour and cook off the flour taste, about 2 minutes whisking constantly. Heat the milk and whisk into the flour mixture, then season with salt and pepper. Add the juice of 1 lemon, stirring frequently. It may look broken, but bring to a simmer and cook until thick, about 2 minutes, stirring until smooth.
Serve on the side for dipping the rolls.
Cook's Note: I grind my own leg of lamb, like my grandmother did. Once I grind the lamb up, I divide it to use in various traditional and not-so-traditional Lebanese cooking. Also, cooking the grape leaves with a lamb chop in the pot helps produce some incredible flavor.