Step 1: In a large, heavy-bottomed pot or Dutch oven, melt the unsalted butter over medium heat. Add the finely diced yellow onion and celery, and sauté gently until they are softened and translucent, about 5-7 minutes. Do not let them brown.
Step 2: Sprinkle the all-purpose flour over the softened vegetables. Cook, stirring constantly, for 2-3 minutes to create a smooth roux. This step is crucial for thickening the soup and eliminating any raw flour taste. The roux should be pale, not browned.
Step 3: Gradually whisk in the whole milk, then the heavy cream, and finally the chicken broth (or seafood stock) into the roux. Whisk continuously to prevent lumps from forming. Bring the mixture to a gentle simmer over medium heat, stirring occasionally. Once it begins to simmer, reduce the heat to low and cook for 10-15 minutes, allowing the soup to thicken slightly and the flavors to meld.
Step 4: Carefully fold in the picked lump crab meat. If using, gently stir in the crab roe. The roe will dissolve into the soup, imparting a beautiful color and a distinctive depth of flavor that is essential to an authentic she crab soup recipe.
Step 5: Season the soup with ground mace (or nutmeg), white pepper, and a pinch of cayenne pepper if you like a little heat. Taste and adjust salt as needed. Remember that the chicken broth can add salinity, so season judiciously.
Step 6: Just before serving, stir in the dry sherry. The sherry adds a signature nutty, slightly sweet complexity to the she crab soup recipe. Start with 2 tablespoons and add more to taste, depending on your preference. Do not boil the soup after adding the sherry, as this can cook off its delicate flavor.
Step 7: Ladle the hot she crab soup into bowls. Garnish each serving with a sprinkle of fresh chopped parsley or chives. Serve immediately with crusty bread or oyster crackers and enjoy this luxurious she crab soup recipe!