1.Melt 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. 2.Uncover 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. 3.Spoon The Hot Mushroom Mixture Onto The Split Hoagie Roll, And Serve.