Preheat the oven to 200°C fan / 425°F and line a large baking tray with baking paper.
Slice the head off the garlic bulb to expose the cloves, then add the bulb to the tray. Drizzle the bulb with a glug of olive oil, then wrap the bulb in baking paper. Roast for 20 minutes.
Add the miso paste, smoked paprika, ground cumin, 3 tbsp of olive oil, 1 tsp of freshly ground black pepper and a pinch of salt to a bowl. Mix, then stir in splashes of water until you have a smooth paste.
Remove any dirt from the mushrooms, then brush them all over with the miso mixture (in the gills and over the caps). Add the mushrooms to the tray with the garlic, gills facing up - and roast for 25 minutes, flipping the mushrooms halfway through. When they’re done, brush any of the juice from the bottom of the tray all over the mushrooms.
Meanwhile, make the chimichurri. Add the parsley, chilli, shallot, dried oregano, red wine vinegar and a pinch of salt to a bowl. Mix, then stir in 5-6 tablespoons of olive oil until the dressing runs smoothly off a spoon.
Finally, add the butter beans to a blender along with the lemon juice and pinches of salt and pepper. When the garlic and mushrooms are ready. Remove the garlic bulb from the tray and squeeze the cloves into the blender, along with 3-4 tablespoons of hot water. Blend, then keep adding hot water until the purée reaches a silky smooth consistency.
To serve, spoon the purée onto plates, top with the roasted mushrooms, then spoon over the chimichurri and serve with torn crusty bread.