When you’re ready to serve, gently reheat the mushrooms and fried sprouts, and heat another frying pan for the eggs. Add the remaining butter and gently fry the eggs until the whites are set but the yolks are still runny. To serve, put the eggs onto warm plates, then spoon over the mushrooms and sprouts. Dress the sprout leaves in 1 tsp olive oil and a pinch of salt and sprinkle onto each plate. Pipe or place the pickled walnuts on the sprout leaves, grate over the truffle using the finest grater you have, or drizzle over truffle oil.