Stir the softened butter and harissa paste together until well combined.
Taste the harissa paste you are using for seasoning – you may or may not need to add a little extra salt and pepper.
Preheat oven to 200°C with the fan on.
Line a large baking tray with baking paper.
Place portabellos on prepared tray and brush generously with harissa butter
Roast for about 7-10 minutes or until just tender.
While the mushrooms are roasting, warm or toast some flatbread and prepare the other toppings.
Serve harissa butter mushrooms piled onto warm flatbread with generous dollops of the spicy lemon yoghurt.
Scatter everything with fresh coriander leaves and pickled onions.
Squeeze over some fresh lime juice and enjoy!