Chipotle mushroom and black bean burgers with peanuts and lime

50g smooth peanut butter

1 x 400g tin of black beans, drained, but not rinsed

2 small cloves of garlic, peeled

2 tsp chipotle chilli flakes

1 tsp ground cumin

1 tbsp olive oil

1 heaped tbsp rye flour

1 lime, zest only

1 tsp sea salt flakes

250g chestnut mushrooms

To serve:

1 lime, cut into 4 wedges

a handful of chopped salted peanuts

a handful of chopped fresh coriander

4 burger buns