1. Preheat the oven to 450ºF. Sauté onion and garlic in olive oil, over medium heat, until translucent, about 2 minutes. Add the mushrooms and sauté until soften, about 4 minutes. Remove from the heat, toss with parsley and mint. Season with salt and pepper, set aside.
2. Season the lamb and sear it over high heat in canola oil, about 3 minutes per side. Remove and cut lambs into 2-inch thick slices.
3. Stack 3 phyllo rectangles and brush the top layer with melted butter. Spoon mushroom into the middle of the rectangle. Top with a medallion of lamb and several pieces of Castello Crumbled Blue Cheese. Roll the phyllo dough around the filling, twisting the ends closed. Continue until all the lamb and mushroom mixture is wrapped inside the phyllo.
4. Bake for pastry is crisp, about 8 minutes. Serve while hot!