Heat a smoker to 250°F. Add your preferred smoking wood according to the smoker’s directions.

Warm the olive oil in a skillet over medium heat. Add the chopped mushrooms and cook for 6 to 8 minutes, stirring occasionally, until softened and their released liquid has cooked off. Let them cool slightly.

In a large bowl, combine the ground beef, egg, panko, ¼ cup milk, kosher salt, black pepper, and Worcestershire sauce. Mix gently just until combined. Fold in the cooled mushrooms, crumbled bacon, and shredded Swiss cheese.

Shape the mixture into a compact loaf and place it on a smoker-safe tray or a sheet of foil with room around the sides for smoke to circulate. Smoke until the center reaches 160°F, checking with an instant-read thermometer.

While the meatloaf smokes, put the potatoes and garlic cloves in a saucepan and cover with water. Bring to a boil, then reduce the heat and simmer until the potatoes are fork-tender, about 15 to 20 minutes. Drain well.

Mash the potatoes and garlic with the butter, warm milk, ½ teaspoon salt, and ¼ teaspoon black pepper. Keep the mash covered while the meatloaf finishes cooking.

Remove the meatloaf from the smoker and let it rest for 10 minutes before slicing. Serve with the garlic mashed potatoes.