Bring 2 Cups of Root Beer to a boil in a medium sauce pan over high heat until reduced by half; approximately 15 minutes. Reduce heat to medium-low and stir in Ketchup, Brown Sugar, Apple Cider Vinegar, Black Pepper, Ground Ginger and Salt. Simmer, stirring frequently, until sauce thickens; approximately another 15-20 minutes. Turn off heat and set aside. For best results, make sauce a day or two beforehand.
In a medium skillet over medium-high heat, brown the Ground Beef, White Onion and Green Bell Pepper; drain off liquids. Stir in the Garlic Powder, Prepared Yellow Mustard, and Root Beer Sauce. Reduce heat and cover, simmer for 30 minutes. Season with salt and pepper to taste.
While the meat mixture is simmering, preheat your oven broiler. Cut the Whole Wheat Dinner Buns in half and brush with melted butter. Toast underneath your oven broiler until lightly brown; keep a very close eye on this, it doesn’t take long.