Make the slaw. Use a mandolin to thinly shave the cabbage and fennel.
Roughly chop the dill. Finely chop the garlic and set aside.
In a bowl, whisk together the olive oil and lemon juice with salt and pepper. Toss together with the cabbage and fennel and dill and set aside.
In a small bowl, mix together the butter, garlic and thyme until smooth.
Spread each mushroom generously with the butter mixture and place under a hot grill. Cook until the mushrooms are tender.
Meanwhile, toast the burger buns.
Slice the avocado. Cut the halloumi into slices.
Heat a large frying pan over a medium high heat, add a little oil to the pan and then fry the halloumi slices until golden brown on either side. Remove to a plate, keep warm and set aside.
Spread the red onion marmalade generously on each of the buns, top with the mushrooms, halloumi slices, slaw, rocket leaves, sprouts and avocado. Top with burger bun tops and serve.
Notes
A “burger” with a difference and one of my favourite ways to enjoy garlic mushrooms- sandwiched between toasted brioche buns with salty haloumi cheese and sweet onion marmalade.