Prep. Preheat oven to 425F and set a large pot of water on the stove to boil.
Prep the pumpkin. Cut a circle in the top of the pumpkin around the stem large enough for your hand to fit through. Remove all seeds and stringy insides of the pumpkin. Using a fork or paring knife, pierce the inside and outside of the pumpkin in several places to allow for faster roasting.
Roast the pumpkin. Add the bourbon to the bottom of the pumpkin if using. Rub the inside walls of the pumpkin with brown sugar. Place in a lipped baking dish, cast iron pan, or pie plate. Bake for 35 to 40 minutes or until the pumpkin is almost cooked through.
Make the stuffing. Dice Yukon gold potatoes, add to boiling water and cook until fork-tender. Drain and set aside. In a large skillet, melt 1 tablespoon of butter. Sauté diced onions until translucent. Add ground beef, season with salt, pepper, and garlic powder. Stir frequently to break up the meat. Using a large dinner fork or wooden spatula, add the potatoes and mash into the beef and onion mixture. Mix the potatoes and ground beef together.
Stuff the pumpkin. Scoop stuffing into the roasted pumpkin. If some of the stuffing fills above the pumpkin, that is fine. Replace the top, return to a 375F oven, and bake for 20 minutes.
Serve. Either cut into slices or scoop out the stuffing and pumpkin. Cutting makes for a more eye appealing presentation, but scooping out the stuffing and roasted pumpkin it is usually served.