Crab Gratin with Potatoes, Leeks, and Spinach

Prepare a medium heat fire (375°F) in a wood-fired oven or cooker.

Heat half of the olive oil in a small skillet over medium heat and sauté the leeks until wilted, about 7 minutes. Blend together with the crabmeat, mustard, chili powder, and Worcestershire sauce in a bowl and set aside. Heat the remaining olive oil in a saucepan over medium heat and sauté the spinach until most of the moisture has evaporated. Stir in the tarragon, salt, and white pepper. Remove from the heat, stir in the crab mixture, and set aside.

To make the Mornay sauce, melt the butter in a skillet over medium heat. When it has stopped foaming, stir in the flour and cook, stirring, for 3 minutes. Whisk in the milk, nutmeg, zest, salt, and pepper. Add the Gruyère and sherry. Cook, stirring, until thickened. Remove from the heat and set over a pot of simmering water.