Grilled Italian Hamburgers

3 pounds lean ground beef

1 pound bulk sweet Italian sausage

1 tablespoon minced onion

1 teaspoon minced garlic

2 teaspoons Italian seasoning

1 tablespoon light olive oil

1 teaspoon salt

1 teaspoon ground black pepper

2 teaspoons anise seed

¼ cup melted butter

6 baguettes (14 to 16 inches), halved crosswise and split

Mix the ground beef, sausage, onion, garlic, Italian seasoning, olive oil, salt, pepper, and anise seed together in a bowl until thoroughly combined. Chill in refrigerator at least 1 hour. Mix again after refrigerating. Divide the mixture into 12 portions and form into oblong burgers with rounded edges, approximately 4 inches wide and 12 inches long. They should be somewhat thin.

Preheat an outdoor grill for medium heat, and lightly oil the grate. Also, preheat an oven to 250 degrees F (120 degrees C). Lightly brush the butter over the cut sides of the baguettes.

Cook on the preheated grill until the burgers are cooked through, 7 to 8 minutes per side. An instant-read thermometer inserted into the center should read 160 degrees F (70 degrees C). About 5 minutes before the meat is finished, lay the open baguette halves on the grill and brown each side until toasted. Place each burger into the baguette, close the baguette, and then wrap snugly with aluminum foil.

Bake the wrapped sandwiches in the preheated oven for 15 minutes before serving.