Open 2 x 400g cans of butterbeans and rinse the beans in a sieve under cold running water, then tip them into a saucepan. Pour in 100ml of water and bring to the boil, then lower the heat and let the beans simmer for 10 minutes in order to heat them through.
Thickly slice 100g of fresh shiitake mushrooms. Cut 100g of chestnut mushrooms into quarters. You will also need 150g of small wild or cultivated mushrooms, left whole.
Melt 30g of butter with 3 tbsp of olive oil in a shallow pan. Add first the chestnut mushrooms, then the shiitake mushrooms then, finally, the whole wild mushrooms, letting them cook to tenderness over a moderate heat.
Chop a small bunch (5g) of chives and add them to the mushrooms along with 12 chopped mint leaves and continue cooking for a minute or two. Season with salt, a little black pepper and a squeeze of lemon juice.
When the butterbeans are hot, pour 100ml of double cream into the mixture and then add 30g of butter. Mash it to a thick purée. I do this in the food processor, but you could use a potato masher or a fork if you prefer.
Season carefully, then spoon the mashed beans on to a couple of shallow bowls or plates, then divide the mushrooms, together with any cooking juices, on top. A trickle of fruity olive oil at the end is a sound touch. Serves 2.
Cutting the mushrooms into different shapes – quarters, slices, nuggets – gives a pleasing assortment of textures. I stick to the cheaper varieties. Expensive wild mushrooms tend to lose their subtle characters when cooked with others.
Cannellini and haricot are other possibilities if you prefer them to butterbeans. You could add cubes of pancetta, fried at the start, to the mushrooms. Let them cook for 3 or 4 minutes, until the fat is translucent, before you add the mushrooms.