Smash Burgers

british beef 70.0% , british dry aged beef 20.0% , unsalted butter 5.4% , potato starch 2.3% , rice flour 1.2% , marrow stock 0.6% , salt 0.3% , yeast extract 0.1% , dextrose 0.1% , flavouring 0.0% , onion 0.0% , Preservative 0.0% , cracked black pepper 0.0% , Antioxidant 0.0% , onion oil 0.0% , garlic puree 0.0%