Mix the lemon zest, paprika, 3/4 teaspoon kosher salt, 1/2 teaspoon black pepper and minced garlic in a medium-sized bowl. Add the shrimp and stir to coat the shrimp with the mixture.
Melt butter in a large, heavy pot over medium heat. When it’s foaming, add the shrimp (and any seasonings left in the bowl) and cook, stirring occasionally, until shrimp is pink and starting to curl, 3 or so minutes. Using a slotted spoon, transfer shrimp to a bowl. Set aside.
Add shallots to the pot and cook until they’re softened, 4 to 5 minutes, stirring occasionally. Add beans and chicken broth and bring to a boil over high. Lower heat and simmer, 8 to 10 minutes.
Stir in reserved shrimp and any juices from the bowl, and cook for another 2 minutes to warm the shrimp through. Stir in parsley (if using) and lemon juice, and adjust seasonings with salt and pepper. Serve with toasted bread.