Pick over the crab at least twice for shells and cartilage.

Bring a large pot of salted water to a boil. Have ready a medium bowl of ice water. Add the spinach to the boiling water and cook until just tender and still bright green, about 1 minute. Drain and transfer to the ice bath. When cool, drain again; use your hands to squeeze out excess water.

Chop the spinach, transfer to a bowl, and gently fold in the crab, egg, flour, cayenne, nutmeg, white pepper, and 1½ teaspoons salt. Using your hands, form the mixture into small, wine-cork-size dumplings.

Heat a sauté pan over medium-high heat. Drop in a generous piece of butter, swirl the pan to coat, and allow it to foam. Roll the dumplings in a small amount of flour, shaking off excess, and cook as many dumplings as will comfortably fit in your pan, being careful not to crowd them. Cook until lightly browned, turning as needed, about 6 minutes. Use a slotted spatula to transfer the dumplings to a platter (or hold them in a low oven to keep them warm).

Finish the dumplings with a drizzle of beurre blanc and serve.

Beurre Blanc

Simmer the wine and salt in a small, nonreactive heavy saucepan until about 2 tablespoons of liquid remain. Slowly whisk in 2 cube of butter at a time, waiting to add the next until each is fully incorporated. Add the lemon juice and parsley; serve immediately.