Spread your bread with mustard. Set aside.
Place 2 luncheon slices side by side in the center of the pan and quickly fry over high heat. Top with the other 2 slices, flip and place cheese slices over the cooked meat.
Crack 2 eggs in a bowl, beat and pour around the luncheon and cheese.
Place both slices of bread, mustard side down, over the cheese and flip the 'pancake' upside down so the bread is now on the pan.
Add 2 more cheese slices in the middle of the pancake, top with a dollop of mayo and some sriracha.
Fold the edges of the omelette over the cheese, flip one slice of bread over the other to 'close' the toastie, place on a plate and slice in half.
Serve piping hot for maximum ooze.