1/2 cup dry sherry
1/2 cup whole milk (OR 3 Tbsp cream with 5 Tbsp water)
1 Tbsp minced garlic
1 Tbsp minced shallots
1 bay leaf
1 Tbsp unsalted butter
1 Tbsp flour
1/2 pound (2 sticks) unsalted butter
1/2 teaspoon salt
1/2 teaspoon white pepper
1 Tbsp lemon juice
Simmer and reduce the liquids, with garlic, shallots, and bay leaf: Place first six ingredients (clam juice, sherry, whole milk, garlic, shallots, bay leaf) in a small saucepan. Heat on medium high heat and let simmer until the liquids have reduced by about half. Make a roux: In a separate saucepan (1-qt minimum) prepare the roux. Heat one tablespoon of butter in the saucepan on medium heat until it is foamy. Sprinkle in the flour, stirring a couple of minutes with a metal whisk until well mixed (tan, but not browned). Slowly add liquid mixture to roux: Slowly add the reduced mixture to the roux, stirring quickly to incorporate. When you first add some of the mixture, the roux will bubble up. Just keep adding the mixture and keep whisking to incorporate. Slowly incorporate butter, 2 Tbsp at a time: Lower the heat to low. Remove the bay leaf. Slowly whisk in the butter, 2 tablespoons at a time. Let the butter tablespoons fully melt and be incorporated into the sauce before adding more tablespoons. Stir in lemon juice, salt, and white pepper. Add some more clam stock or water if the sauce is too thick.