The perfect hamburger

"That," said Mr Borthwick, "was the best hamburger I've ever tasted!" Joe has just created the yummiest, juciest, most delicious hamburger ever - and his friend Mr Borthwick wants to sell it in his new hamburger shop. But there's a problem - Joe has completely forgotten the recipe and the shop is opening very soon. A pinch of this, a touch of that and a spoonful of something else... the race is on for Joe to remember!