Homemade Brioche Burger with Caramelized Onions

Slice two large red onions into thick rings.

Finely mince 400g of sirloin steak with a knife to preserve its texture.

Season the minced beef with salt and pepper, and mix well.

Divide the beef into two portions, shape them into patties by hand, and press the center to prevent them from puffing up.

Slice the two brioche hamburger buns in half.

Toast the hamburger buns in a hot, dry pan until golden brown.

Add olive oil to a pan, add the sliced onions and a pinch of salt. Sauté until the onions are translucent.

Add balsamic vinegar and sugar to the onions. Continue to sauté until the liquid has completely reduced and the onions are caramelized.

In a clean pan, add a little olive oil and sear the patties on high heat on both sides until browned.

Preheat the oven to 220°C. Top the seared patties with Gruyère cheese.

Bake the cheese-topped patties in the oven at 200-220°C for 10 minutes until the cheese is perfectly melted.

Spread mayonnaise and whole-grain mustard on the toasted buns.

Assemble the burger by placing the cheesy patty on the bottom bun, topping generously with the caramelized onions, and covering with the top bun.