Rinse 2 cups of Calrose rice under hot water until water runs clear, then cook according to package instructions. Let steam for 10 minutes after cooking.

Whisk together 1/4 cup dark brown sugar, 1/4 cup soy sauce, 2 tablespoons mirin, and 1 tablespoon sesame oil until smooth. Microwave for 30-45 seconds until sugar dissolves.

Preheat a skillet over medium-high heat. Slice Spam into 8 pieces, then cook for 2-3 minutes per side until golden brown. Drizzle teriyaki sauce over Spam and caramelize for 1 minute.

Lay a sheet of sushi nori shiny side down. Position the musubi mold on the nori to shape the Spam Musubi.

Scoop sticky rice into the mold halfway, pack it down, sprinkle with furikake, and place 2-3 slices of Spam on top.

Press the lid down gently to form the musubi. Wrap nori around and seal edges with water.

Repeat with remaining rice and Spam adjusting quantities as needed.

Slice each musubi in half with a warm knife to showcase layers and serve immediately or pack for later.