Garlicky Shrimp with Bread Crumbs

3 inch piece baguette , cut into small pieces
5 tablespoons unsalted butter , cut into 5 pieces
1 small shallot , minced (about 2 tablespoons)
Table salt and ground black pepper
2 tablespoons minced fresh parsley leaves
2 pounds extra-large shrimp (21-25), peeled and deveined
1/4 teaspoon sugar
4 teaspoons vegetable oil
4 medium cloves garlic , minced or pressed through a garlic press (about 4 teaspoons)
1/8 teaspoon red pepper flakes
2 teaspoons unbleached all-purpose flour
1/3 cup dry sherry
2/3 cup clam juice (bottled)
2 teaspoons fresh lemon juice
1 lemon , cut into wedges

1. Pulse bread in food processor until coarsely ground; you should have about 1 cup crumbs. Melt 1 tablespoon butter in 12-inch nonstick skillet over medium heat. When foaming subsides, add crumbs, shallot, 1/8 teaspoon salt, and 1/8 teaspoon pepper. Cook, stirring occasionally, until golden brown, 7 to 10 minutes. Stir in 1 tablespoon parsley and transfer to plate to cool. Wipe out skillet with paper towels.

2. Thoroughly dry shrimp with paper towels; toss with sugar, 1/4 teaspoon salt, and 1/4 teaspoon pepper in bowl. Return skillet to high heat, add 2 teaspoons oil, and heat until shimmering. Add half of shrimp in single layer and cook until spotty brown and edges turn pink, about 3 minutes (do not flip shrimp). Remove pan from heat and transfer shrimp to large plate. Wipe out skillet with paper towels. Repeat with remaining 2 teaspoons oil and shrimp; transfer shrimp to plate.

3. Return skillet to medium heat and add 1 tablespoon butter. When melted, add garlic and pepper flakes; cook, stirring frequently, until garlic just begins to color, about 1 minute. Add flour and cook, stirring frequently, for 1 minute. Increase heat to medium-high and slowly whisk in sherry and clam juice. Bring to simmer and cook until mixture reduces to 3/4 cup, 3 to 4 minutes. Whisk in remaining 3 tablespoons butter, 1 tablespoon at a time. Stir in lemon juice and remaining tablespoon parsley.

4. Reduce heat to medium-low, return shrimp to pan, and toss to combine. Cook, covered, until shrimp are pink and cooked through, 2 to 3 minutes. Uncover and sprinkle with toasted bread crumbs. Serve with lemon wedges.