Add 1 teaspoon of olive oil to a large skillet. Add sausage links and brown for 6-8 minutes per side or until cooked through. Remove from heat and set aside.

Add shallot and garlic to pan, cook for 1-2 minutes or until soft, stirring as they cook. Add both peppers to pan. Continue to cook vegetables for another 4-5 minutes or just until they begin to soften but still have some bite to them.

Stir in crushed tomatoes, tomato paste, sugar, oregano and basil. Add Harissa if using. Stir. Let sauce simmer for additional 5 minutes.

Cut sausage links on the bias into 3 chunks per link. Add sausage to sauce and let sausage cook another 5 minutes.

Cut sub rolls open, but do not slice all the way through. Fill each roll with sausage and peppers. Arrange subs on a baking sheet and preheat your oven to broil.

Top subs with shredded cheese and broil until cheese is bubbly about 2-3 minutes. Top with fresh basil right before saving.