Preheat oven to 400 degrees F. Grease a 9×13-inch casserole dish.
Poke a few holes into each potato using a toothpick.
Bake potatoes in the preheated oven until fully cooked, about 1 hour. Cool for about 15 minutes.
Place the bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain the bacon slices on paper towels and crumble.
Cut a thin slice from one side of each potato; carefully scoop out the flesh and transfer to a bowl. Discard skins. Mix 3/4 cup Cheddar cheese, sour cream, milk, butter, chives, salt, black pepper, and garlic powder with potatoes. Spread potato mixture into the prepared casserole dish; top with 3/4 cup Cheddar cheese and crumbled bacon.
Bake in the preheated oven until just bubbling, 10 to 15 minutes. Cool for at least 5 minutes before serving.
Notes
Tips:
If you want to save time on the day of serving, you can prepare this casserole a day ahead. Simply follow the recipe until Step 7, cover the baking dish with aluminum foil, and refrigerate. When you're ready to serve, preheat your oven to 350 degrees F (175 degrees C) and bake the casserole, still covered with foil, for approximately 40 minutes. Then remove the foil and bake for an additional 15 minutes, or until the cheese is melted and bubbly.
Feel free to customize this recipe by adding your favorite toppings or ingredients. You can sprinkle some chopped green onions, diced tomatoes, or even jalapeños on top for an extra kick of flavor. Get creative and make it your own!