In a small sauce pan, over a medium heat, brown the mushrooms in a 25g of unsalted butter or oil for two minutes.
Remove eight mushrooms and keep to one side for the burger.
Add the garlic and onion until soft and translucent (about five minutes).
Before the onions brown add in the milk and thyme leaves and reduce by half.
Pass the sauce through a sieve. Blend the mushroom onion mix and slowly add the milk back in until you reach a nice consistency similar to custard. Season appropriately.
Slice the bun in half and toast both sides.
Spread ½tsp of jelly on the base followed by the mustard, pickles and iceberg.
Place a large dollop (2tbs) of the mushroom puree in the middle of the iceberg and add 4 of the sautéed chanterelles to each burger.
Smash the patties in a hot frying pan in a little oil and season.
Flip them over and place the caramelised onions on one of the patties and top each with 2 slices of cheese.
Place one patty on top of the other (I like to leave the onion one on the bottom for some reason) and the bun on top of that.
Now cloche the burger cheese tower.
Pour 30mls of water into the pan and cover the meat/cheese/bread tower with a tight fitting lid or metal bowl.
Leave it for 30secs then carefully place on top of the base.Leave it to sit for a couple of mins for all the flavours to marry together and enjoy this messy beauty.