Miniature Crab Cakes with Mustard Mayonnaise

For mustard mayonnaise 1/4 cup mayonnaise 2 1/2 teaspoons stone-ground mustard 1/4 teaspoon fresh lemon juice, or to taste 1/2 stick (1/4 cup) unsalted butter, melted In a small non-stick skillet saute bell pepper in oil over moderately high heat, stirring, 2 minutes, or until softened and golden. In a bowl whisk together mayonnaise, yolk, mustard, lemon juice, tarragon, and bell pepper and stir in crab and salt and pepper to taste gently but thoroughly. Chill crab mixture, covered, at least 1 hour. Preheat oven to 350 F. In a large shallow baking pan spread panko in even layer. Toast panko, stirring occasionally, until golden, about 10 minutes, and cool. Form rounded teaspoons of crab mixture into slightly flattened 1-inch rounds and gently coat with panko, transferring to a shallow baking pan. Chill crab cakes, loosely covered with wax paper, at least 2 hours and up to 4. In a small bowl whisk together mayonnaise, mustard, and lemon juice. Preheat oven to 450F. Drizzle a scant 1/4 teaspoon butter on each crab cake and bake in middle of oven until crisp and cooked through, about 15 minutes. Serve crab cakes with mustard mayonnaise.