Joy to the Food

1 Make the onions: Thinly slice the [wprm-ingredient text="1/2 red onion" uid="11"] using a mandolin, if possible. In a large jar or bowl, combine equal parts white vinegar and water (about ¾ cup each, depending on the container size). Add the [wprm-ingredient text="1 tbsp balsamic glaze" uid="14"] and stir. Add the sliced onions, cover, and refrigerate while you prepare the burgers. You can make these up to 2 weeks ahead.
2 Preheat: Heat a grill or skillet to medium-high heat. Set aside half of the Boursin cheese for later. The other half will get stuffed into the burgers!See notes below for how to make these in the oven or on the stove top!
3 Make the burger patties: In a bowl, mix the [wprm-ingredient text="1 pound lean ground beef" uid="1"], [wprm-ingredient text="1 egg yolk" uid="2"], [wprm-ingredient text="1/2 tsp salt" uid="3"], [wprm-ingredient text="1 tsp pepper" uid="4"], and [wprm-ingredient text="½ tsp garlic powder" uid="5"]. Divide into 4 balls, then flatten each slightly and create an indent in the center. Place 1-2 tablespoons of Boursin cheese in the indent for each burger, then carefully wrap the meat around the cheese to form a stuffed patty. It's fine if they are very round, once you put them on the grill, you can flatten them slightly with a spatula.
4 Cook the patties: Cook the burgers on one side for 5-7 minutes, then flip and cook for another 2-3 minutes. Flip once more and cook for an additional 1-2 minutes, or until the internal temperature reaches 145°F (63°C) for medium. If using a skillet, cover with a lid to help the burgers cook evenly.
5 Assemble: On each bun, spread 1-2 tbsp of the remaining cheese on one side. Drizzle balsamic glaze on the other side. Top with the burger patty, pickled red onions, and arugula. Enjoy!