Slice the onion thinly and pat dry with paper towels. Lightly coat with 1 tbsp of flour. Slice the mushrooms into 5mm pieces.

Spread butter inside the hot dog buns.

Heat salad oil in a pan over medium heat. Fry the onion until golden brown and crispy. Drain excess oil with paper towels. In the same pan, cook the sausages until browned and mushrooms until tender with salt and pepper.

Mix pizza cheese, 1 tsp flour, and milk in a microwave-safe bowl. Cover loosely with plastic wrap and microwave at 600W for 1 minute. Stir until smooth to make cheese sauce.