1. For the ketchup, put a pan on the heat, add some olive oil. Finely dice a shallot. Put into the pan and sweat them off. Finely chop some garlic, add some salt to use as an abrasive and purée the garlic, add to the pan. Once softened, add some tinned tomatoes, Worcestershire sauce and maple syrup then break up the tomatoes and allow to reduce & thicken for 30-40 minutes. Once reduced begin with the onion rings.
2. For the batter, in a bowl put some plain flour, yeast and salt and whisk to get rid of any lumps. Pour in the lager a bit at a time and whisk until you have no lumps then rest for an hour. Take the top off the onion and cut thick rings, push the middle out, put onto a tray. Get the rested batter, whisk it to ensure there are no lumps. Dust the onions with flour, mix and drop into the batter and coat them.
3. Take them to the pre-heated fryer at 170°C, carefully drop them in one at a time, keep them moving. After 4-5 minutes take them out of the fryer onto a tray covered in kitchen roll and allow to rest. For the burger take your beef, mould it to the right size/shape touching as little as possible. Oil your hands, not the griddle and coat the burgers in oil. Place them away from you onto the griddle. Sprinkle with salt and pepper. After about two minutes turns them over and season the other side.
4. Take two slices of cheese and lay over the burger and lay another burger on top. Then lay over a slice of American burger cheese. Steam it inside by spraying the griddle with water and putting a saucepan over the top. Take the burger off the heat and rest.
5. Take a bun, cut in half, brush it with melted butter and put onto the griddle and toast for a couple of seconds.
To build the burger, first spread mayonnaise on the top bun, lay on some lettuce, then spread some of the ketchup on the bottom bun. Lift the burger onto it and lay some sliced gherkin on the burger and put the bun lid on.
6. On a board, put the remaining ketchup into a small bowl, then place some onion rings on the board and finally put the burger onto the board.