Waffle Batter

1. Bring the water to a boil with the butter. Off the heat, add the potato starch. Incorporate the eggs, then the mashed potato. Salt lightly.
2. Cook the waffles in a waffle maker as usual.

Garnish and finishing

1. Peel and cut the chervil into quarters. Cook gently in butter. Slice the marrow into rounds; poach in warm water. Slice the truffles into rounds.
2. Emulsify the truffle juice with the butter.
3. Pour the truffle sauce into wide-rimmed bowls. Add the chervil, marrow and truffle slices. Sprinkle with fleur de sel, then place the warm waffles on the edge of the bowls.