To Make Demi-Glace: Heat 2 tablespoons olive oil in a medium skillet over medium heat, and add trimmings from lamb. Season with salt and pepper. Brown the fat, reduce heat, and add 4 cloves minced garlic, onion, carrots, celery leaves, port, red wine, and chicken broth. Transfer the mixture to a slow cooker, and simmer on Low 8 hours, or overnight.

Strain the slow cooker mixture into a saucepan over medium-low heat. Mix in the spearmint, rosemary, and mint jelly, and simmer, adding more port, wine, or broth as needed, until mixture leaves a syrup-like coating on the back of a spoon. Strain once more, and keep warm while lamb roasts.

To Roast Lamb: Place a cast iron or oven-proof skillet in the oven, and preheat to 450 degrees F (230 degrees C). Rub lamb with 2 tablespoons olive oil, salt, pepper, and garlic. Coat with panko bread crumbs.

Carefully remove the heated skillet from the oven, warm 2 tablespoons olive oil in the skillet, and sear lamb on both sides. Return the skillet with the lamb to the preheated oven, and continue cooking 5 to 10 minutes, to an internal temperature of 145 degrees F (63 degrees C).

Pour a small amount of the demi-glace on platter and arrange lamb criss-crossed. Drizzle with more demi-glace, and garnish with fresh mint to serve.