Heat some olive oil in two large frying pans. If you don’t have two large pans, you can also do this in two batches (takes 5 minutes per batch).
Thickly slice the mushrooms and scatter them into the hot pans so that they fry in a single layer (if the pan is too crowded they won’t get golden). Season with 1/4 tsp salt and continue to fry until they are golden brown on both sides.
In the meantime, drain the beans. Spread the toum (or the substitute you’re using) evenly over the toasted sourdough slices and scatter over most of the butter beans, pressing them into the toum as you go. Dot the remianing butter beans around the bread on the plate. Divide the golden mushrooms over the butter beans and top them with a handful of rocket. Drizzle generously with extra virgin olive oil and sprinkle with flakey sea salt and some freshly ground black pepper.
Toum substitute: If you don’t have any toum and no time to make any ahead (there’s a recipe here), you can just use a vegan aioli of your choice instead. Or take 2 tbsp of vegan mayonnaise, grate in 1 small garlic clove and add the juice of half a lemon.