This very delicious recipe is our second favorite shrimp recipe.
Finely chop bread to get 1 c crumbs. Milt 1 tbsp butter in skillet over medium heat. When foaming subsides, add crumbs, leek, 1/8 tsp salt, and 1/8 tsp pepper. Cook until golden brown (7-10 minutes). Stir in 1 tbsp parsley. Transfer to plate to cool and wipe out skillet with paper towels.
Thoroughly dry shrimp with paper towels, toss with sugar, 1/4 tsp salt and 1/4 tsp pepper in bowl. Return skillet to high heat, add 2 tsp oil, heat until shimmering. Add half of shrimp in single layer and cook until spotty brown and edges turn pink (3 mintues). Remove pan from heat and transfer shrimp to large plate. Wipe out skillet with paper towel.
Return skillet to medium heat and add 1 tbsp butter. When melted, add garlic and pepper flakes. Cook stiring frequently until garlic browns. Increase heat to medium-high and slowly whisk in clam juice. Bring to simmer and cook until mixture reduces to 3/4 c (3-4 mintues). Whisk in remining 3 tbsp butter 1 tbsp at a time. Stir in lemon juice and remaining tbsp parsley.
Reduce heat to medium-low, return shrimp to pan, toss to combine. Cook, covered, until shrimp are pink and cooked through (2-3 minutes). Uncover and sprinkle with toasted bread crumbs.