Cook slowly in a large skillet over medium heat until browned and cooked throughout:
Transfer the sausages to a plate. Pour off all but 2 tablespoons of fat from the skillet. Add:
Cook over medium-low heat, stirring often, until the peppers are very soft, about 25 minutes. If desired, stir in:
Return the sausages to the skillet and heat through, about 3 minutes. Place one sausage on each of:
Top with the onions and peppers. Gently press the sandwiches together and serve.