In a large mixing bowl, combine ground American Lamb, breadcrumbs, grated Parmesan cheese, egg, minced garlic, lemon zest, lemon juice, chopped parsley, salt, pepper and chili flakes. Mix until well combined.
Shape the lamb mixture into meatballs, about 1-2 inches in diameter, about 16 meatballs in total.
Place the meatballs on a baking sheet lined with parchment paper and bake in the preheated oven for 15-20 minutes, or until they are cooked through and lightly browned*.
2. Assemble the sandwiches
Preheat the broiler in your oven.
Spread pesto evenly on the top and bottom of each hoagie roll.
Place the cooked lamb meatballs on each hoagie roll. Top the meatballs with a slice of fontina cheese. Place the assembled sandwiches under the broiler for 1-2 minutes, or until the cheese is melted and bubbly. Close the sandwiches with the top half of the hoagie rolls.
USDA recommends ground lamb is cooked to an internal temperature of 160°F