fresh lemon zest and 2 tablespoons juice • sweet or smoked paprika • garlic cloves, grated • Kosher salt and black pepper • peeled, deveined large shrimp (tails removed) • unsalted butter • large onion, chopped • dry cannellini beans or other white beans, cooked and drained or 4 (15 ounce) cans, rinsed • chicken stock or vegetable stock • finely chopped fresh parsley (optional) • Toasted bread, for serving (optional)