1Melt the butter in a skillet with a lid over medium heat, and cook and stir the red shallots, basil, and garlic until fragrant, about 1 minute. Stir in the hot paprika, salt, and pepper. Add the spinach, portabella mushrooms, and yellow bell pepper, stir a few times, cover with lid, and reduce the heat to medium-low. Cook the mixture until the spinach and mushrooms give up their liquid and the peppers are softened, about 4 minutes.
2Uncover the skillet, and pour in the pepper sauce and balsamic vinegar. Increase the heat to medium, and let the mixture cook down and thicken slightly, about 2 minutes.
3Spoon the hot mushroom mixture onto the split hoagie roll, and serve.