Step 1: Prepare the Onions (Two Ways)

• For the patty mixture: Take half of the medium onion and grate it using the large holes of a box grater. This releases the onion's juices and flavor while keeping a finer texture that incorporates well into the meat.
• Set aside the grated onion in a large mixing bowl.
• For the caramelized onion topping: Thinly slice the remaining half of the medium onion and the entire large onion.
• Heat butter in a skillet over medium-low heat until melted.
• Add all the sliced onions and a pinch of salt. Cook slowly, stirring occasionally, for about 15-20 minutes until they turn golden brown and soft. For extra sweetness, add the optional brown sugar during the last 5 minutes of cooking.
• Transfer caramelized onions to a small bowl and set aside.

Step 2: Prepare the Burger Patties

• To the bowl with the grated onion, add the ground beef, minced garlic, Worcestershire sauce, Dijon mustard, salt, and pepper.
• Gently mix with your hands until just combined. The key word is GENTLY – overworking the meat will result in tough burgers!
• Divide the mixture into 4 equal portions and shape into patties about 4-5 inches wide and 3/4 inch thick. Remember that burgers shrink when cooking, so make them slightly larger than your buns.
• Press your thumb into the center of each patty to create a slight dimple. This prevents the burger from puffing up in the middle during cooking.
• If you have time, let the patties rest in the refrigerator for 15-30 minutes. This helps them hold together better during cooking.

Step 3: Cook the Burgers

For stovetop cooking:

• Heat olive oil in a large skillet over medium-high heat until shimmering.
• Place the patties in the skillet without overcrowding (cook in batches if needed).
• Cook for 3-4 minutes on the first side until a nice crust forms.
• Flip once and cook for another 3-4 minutes for medium doneness (internal temperature of 160°F/71°C).
• Add cheese during the last minute of cooking and cover briefly to melt.

For grilling:

• Preheat your grill to medium-high heat (about 400-450°F).
• Lightly oil the grates to prevent sticking.
• Grill the patties for 4-5 minutes on the first side.
• Flip once and cook for another 3-4 minutes for medium doneness.
• Add cheese during the last minute of cooking and close the grill lid to melt.

Step 4: Assemble and Serve

• While the cheese is melting, lightly toast the burger buns on the grill or in a toaster.
• Build your burger: Start with the bottom bun, add lettuce if using (this creates a moisture barrier that helps prevent a soggy bun), then the cheese-topped patty.
• Top each burger with a generous portion of the caramelized onions.
• Add tomato slices, pickles, and condiments of your choice.
• Crown with the top bun and serve immediately while hot.
• Prepare for compliments and requests for the recipe!