– 500 grams 85% lean ground beef forms the base of the juicy patties

– 30 grams shredded frozen butter helps maintain moisture during cooking

– 50 grams finely minced yellow onion adds subtle sweetness and flavor

– 1 teaspoon yellow mustard provides a tangy kick

– 1 tablespoon Worcestershire sauce enhances the savory depth

– 1 clove minced garlic brings aromatic notes

– Salt and pepper to taste seasons the mixture perfectly

– 150 grams thinly sliced yellow onions for caramelizing and building the base

– 30 grams cold unsalted butter used to start the caramelization process

– 240 milliliters chicken broth adds liquid for the sauce

– 240 milliliters beef broth contributes rich flavor

– ½ teaspoon onion powder boosts the onion taste

– ½ teaspoon garlic powder adds extra garlic essence

– 1 tablespoon Worcestershire sauce deepens the umami

– Salt to taste balances the seasoning

– 15 grams cornstarch mixed with water to thicken

– 60 milliliters cold water combines with cornstarch for thickening

– 30 grams cold butter swirled in at the end for a smooth texture