Step 1

Slice the buns with a serrated knife, lengthwise, without cutting them completely apart. Butter the insides of the buns with about 1 tbsp (each) of the softened butter.

Step 2

Heat your griddle or skillet over medium-high heat. Place the buns on the griddle/skillet, cut side down, and cook until toasted and lightly browned, about 3 minutes. Use a spatula to pick them up and set them aside.

Step 3

Add 2 tbsp of the oil to the griddle/skillet and heat until shimmering. Add the onions and sauté, stirring frequently, until very soft and starting to turn brown and caramelize, about 10 to 15 minutes. Use a spatula and spoon to transfer to a bowl.

Step 4

Add another 1 tablespoon of oil to the hot griddle/skillet. Add the sliced meat evenly across the surface. Don't bother them for a minute or so. Then, start to gently stir them around, and cook until almost no longer pink. Add the salt and pepper and stir to combine.

Step 5

Stir in the caramelized onions and cook for about another minute. Separate the meat/onion mixture into 4 mounds that are roughly the length of the bun. Place 3 slices of cheese over each mound, overlapping them. Wait a couple of minutes until the cheese melts.

Step 6

Place the buns, toasted side down, on top of the melty cheese. Use a large spatula (or two) to scoop the meat and cheese mixture into the toasted bun. Spoon in any loose meat into the sandwiches. Serve at once.