Prepare the Muffin Tin: Preheat your oven to 375°F (190°C). Grease a 12-cup muffin tin with butter or oil spray to prevent sticking.

Combine the Ingredients: In a large mixing bowl, add the mashed potatoes, eggs, shredded cheddar cheese, grated Parmesan cheese, green onions, and bacon bits if using.

Season with salt, black pepper, and garlic powder. Stir everything together until well combined.

Fill the Muffin Cups: Scoop the mashed potato mixture into the prepared muffin cups, filling each cup about three-quarters full. Gently press the mixture down to ensure each cup is compact and will hold its shape during baking.

Bake the Muffins: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the tops are golden and slightly crispy. The muffins should be firm to the touch when done.

Cool and Serve: Remove the muffin tin from the oven and allow the muffins to cool for a few minutes. Use a butter knife to gently loosen the edges, then remove the muffins from the tin.

Serve warm, garnished with extra green onions if desired.