Cut the Sundae (Korean blood sausage) into bite-sized pieces.
Cut the mushrooms into eatable pieces.
Slice the onion and green onion.
Heat oil in a pan and sauté the onion and green onion.
Add mushrooms and stir-fry.
Add the sundae and stir-fry together.
Season with salt and pepper to taste.
Serve the finished dish on a plate.