1. Combine first 6 ingredients in a small saucepan over low heat, stirring well with a whisk. Add butter; stir until butter melts. Keep warm.
2. Add water to a large skillet, filling two-thirds full. Bring to a boil; reduce heat, and simmer. Add 1 tablespoon white wine vinegar. Break each egg into a custard cup, and pour gently into pan. Cook for 3 minutes or until desired degree of doneness. Place 1 muffin, cut sides up, on each of 4 plates, and divide crab among muffins. Remove eggs from pan using a slotted spoon. Gently place 1 egg on each muffin half. Top each serving with about 3 tablespoons sauce. Sprinkle with cracked pepper. Garnish with chives and tarragon, if desired.