Preheat oven to 400°.
Place bread in a food processor, and pulse 10 times or until coarse crumbs measure 1 cup.
Melt 1 tablespoon butter in a large nonstick skillet over medium-high heat. Add half of garlic; sauté 30 seconds. Add breadcrumbs, 1 1/2 teaspoons tarragon, and 1 1/2 teaspoons green onions; cook 2 minutes, stirring constantly. Place breadcrumb mixture in a bowl.
Add remaining 1 tablespoon butter to pan; cook 1 minute or until butter begins to brown. Add remaining half of garlic; sauté 30 seconds, stirring constantly. Add shrimp; sauté 2 minutes. Stir in dry vermouth and Dijon mustard; simmer for 1 minute or until the shrimp are done. Stir in remaining 1 tablespoon tarragon, remaining 1 tablespoon green onions, salt, and pepper.
Arrange the shrimp mixture in a single layer in an 8-inch square baking dish, and sprinkle breadcrumb mixture evenly over shrimp. Bake at 400° for 10 minutes or until the breadcrumbs are golden.