Preheat Oven: Heat to 350°F (175°C) before starting.
Mix Sausages: Blend mild and hot Italian sausage, garlic, fennel, seasoning, and bread crumbs in a big bowl.
Shape Patties: Make 12 patties, and place them in a pan.
Make Sauce: Combine tomatoes, onions, mushrooms, olives, garlic, water, oil, paste, herbs, mustard, and pepper.
Pour Sauce: Pour sauce mix over patties, add pepperoni and parsley on top.
Bake: Cook for 40 mins till browned and done.
Prep Veggies: Sauté onions, and peppers in melted garlic butter.
Prepare Bread: Cut French bread slices.
Shred Cheese: Grate mozzarella for each sandwich.
Serve: Once Hot Dagos are cooked, create sandwiches: Place patty on a French bread slice, add sautéed onions, bell peppers, Mozzarella cheese, and top with another bread slice. Serve promptly while warm!