In a large saute pan, cook onions and sausage on high heat for about 5 minutes, until meat is browned and onions are tender.
Add garlic and cook for about 40 seconds, until fragrant.
Add crushed tomatoes, beef stock, and fresh basil. Stir together until basil is wilted.
Place mixture into a large bowl with rice, hot sauce, and mozzarella cheese. Stir well to combine. Season with salt and pepper.
Evenly add stuffing to peppers, leaving leftover stuffing in fridge for later on in the week. In olive oil in another big saute pan on medium-high heat, cook peppers until they soften and begin to slightly char. (You could also bake these as well.)