Spicy miso mushroom burger

Ingredients

• 2 portobello mushrooms
• 2 whole wheat buns, grilled
• 1 tbsp brown rice miso
• 1 tbsp sesame oil
• 1 tbsp sriracha
• 1 cucumber, cut into ribbons
• 1 carrot, grated
• 2 tsp vinegar of choice
• 2 spring onions
• 2 tsp toasted sesame seeds
• 1 avocado, cubed
• a pinch of chilli flakes
• juice of 1/2 a lime
• pickled gherkins (optional)