Finely chop the Spam and onion.
In a bowl, combine the chopped Spam, chopped onion, minced garlic, breadcrumbs, egg, and pepper. Mix well.
Shape the mixture into round, flat patties.
Heat oil in a pan and cook the patties on medium-low heat until golden brown on both sides.
Place the patties on a plate and pour demi-glace sauce over them.