In a large skillet over medium heat, add your olive oil and saute your diced onions for 3 minutes. Add in your minced garlic and saute for an additional minute.
To the skillet, add in the ground beef. Take a wooden spoon and begin to crumble and brown ground beef. This should take about 5 minutes. Drain off any excess fat from your skillet.
To the skillet, add in your Worcestershire sauce, yellow mustard, sugar, pickle juice, beef broth, salt, and pepper. Allow the mixture to come up to a simmer. Once the beef mixture simmers, lower the heat and allow the beef broth to be cooked down by half. This should take about 30 minutes.
On the bottom half of your toasted bun, using a slotted spoon, pile meat onto the bun along with a slice of cheese, chopped pickles, and a squirt of mustard. Top with the other half of the bun and enjoy!