Vegetarian dish. Peel the shallot and cut into thin slices. Marinate in the vinegar and chill.
Pull the mushrooms apart using a fork and fry them in a pan with a little oil over a high heat. Do not stir them too vigorously, otherwise too much liquid will seep out.
Peel the shallots and garlic clove and dice very finely. Add to the mushrooms and fry until everything turns a nice brown colour.
Add the tomato paste and fry briefly. Pour in the vegetable stock, bring to the boil and then turn the heat down.
Next add the soy sauce, apple cider vinegar, ketchup, paprika powder, chilli flakes, salt and black pepper and cook for 25-30 minutes until a thick sauce forms.
Heat some butter in a frying pan, slice the burger buns and place them cut-side-down in the pan. Quickly fry until brown and put to one aside.
Thinly slice the gherkins and put to one side.
Fill the burger buns with coleslaw, the pulled mushrooms and gherkins and serve immediately.