Step 1

Add the butter to a large skillet set over medium heat. Once melted add the onions, tossing to coat. Spread them out in an even layer.

Step 2

Let the onions cook for 8-10 minutes. Flip them over and continue cooking another 8-10 minutes, stir the onions well. Reduce the heat to medium low and cook another 8-10 minutes, stirring occasionally, just until the onions have caramelized. Set aside.

Step 3

Add the ground beef, seasonings, and Worcestershire sauce to a mixing bowl. Mix them together until thoroughly combined.

Step 4

Transfer the caramelized onions to a bowl, and using a paper towel- carefully wipe the skillet clean. Set the skillet over medium high heat.

Step 5

Divide the meat mixture into 4 roughly even balls. Flatten each one out to form a patty that's loosely the size/shape of your sliced bread. Add the patties to the hot skillet, and let them cook for 4-5 minutes before flipping and continuing to cook another 4-5 minutes, or until cooked to your preferences.

Step 6

Carefully remove the hot patties from the skillet and transfer them to a waiting plate. Set aside.

Step 7

Butter the outsides of your bread, then add them to the skillet. Working quickly and carefully, top each of the bottoms with thousand island spread to the edges, a hamburger patty, 1/4 of the caramelized onions, and two slices of Swiss. Close each sandwich by adding the other side of bread- buttered side up.

Step 8

Cook until the bottom slice of bread is golden brown. Using two spatulas, carefully hold the sandwiches together and flip them. Continue cooking until the other side's also golden brown, and the cheese has melted. Press down gently on the tops to 'glue' them together before removing from the skillet.

Step 9

Serve warm with additional dressing on the side for dipping.