Step 1: Preheat oven to 375°F (190°C). Lightly grease a 12-cup muffin tin.
Step 2: In a large bowl, combine ground beef, breadcrumbs, egg, diced onion, minced garlic, Worcestershire sauce, smoked paprika, salt, and pepper. Mix gently until just combined (do not overmix).
Step 3: Divide the meatloaf mixture evenly among the 12 muffin cups, pressing firmly to form compact "cupcakes."
Step 4: Bake for 20-25 minutes, or until cooked through. Drain any excess fat.
Step 5: While the meatloaf bakes, prepare the glaze: In a small saucepan, whisk together ketchup, brown sugar, apple cider vinegar, and bourbon. Bring to a simmer over medium heat and cook for 5-7 minutes, stirring occasionally, until slightly thickened.
Step 6: Remove meatloaf cupcakes from the oven. Brush a generous amount of the bourbon BBQ glaze over the top of each meatloaf cupcake. Return to the oven and bake for another 5-10 minutes, or until the glaze is bubbly and slightly caramelized.
Step 7: While the glazed meatloaf bakes, prepare the mashed potatoes: Place peeled and quartered potatoes in a large pot and cover with cold, salted water. Bring to a boil and cook for 15-20 minutes, or until fork-tender. Drain well.
Step 8: Return hot potatoes to the pot. Add milk and butter. Mash until smooth and creamy. Season with salt and pepper to taste.
Step 9: Carefully remove the meatloaf cupcakes from the muffin tin and place them on a serving platter.
Step 10: Transfer the mashed potatoes to a piping bag fitted with a star tip (or use a Ziploc bag with a corner snipped off). Pipe a swirl of mashed potatoes on top of each meatloaf cupcake, resembling frosting.
Step 11: Serve immediately and enjoy your savory "cupcakes"!