Preheat oven to 375°.
To prepare boules, hollow out each roll, leaving about a 1/4-inch-thick shell; reserve torn bread for another use. Place bread shells on a baking sheet. Bake at 375° for 5 minutes. Remove from oven; set aside.
To prepare deviled crab, combine 2 tablespoons chopped green onions, 1/4 cup wine, and garlic in a small saucepan; bring to a boil. Reduce heat; simmer until reduced to 2 tablespoons (about 2 minutes). Remove from heat; stir in mayonnaise, mustard, red pepper, and paprika. Add 2 tablespoons chopped green onions and crab; toss gently to combine. Spoon crab mixture evenly into bread shells. Bake at 375° for 15 minutes or until thoroughly heated.
To prepare beurre blanc, combine 2 tablespoons broth, shallots, 1/4 cup wine, vinegar, and bay leaf in a small saucepan; bring to a boil. Reduce heat, and simmer until reduced to 1/4 cup (about 3 minutes). Drain through a fine sieve into a bowl, reserving liquid; discard solids.
Return wine mixture to pan. Combine remaining broth and cornstarch, stirring well with a whisk; stir into wine mixture. Bring to a boil; cook 1 minute, stirring constantly. Remove from heat; add butter, stirring until butter melts. Stir in juice and black pepper. Serve beurre blanc immediately over warm boules. Garnish with julienne-cut green onions, if desired.