Croquettes (croquetas) are traditionally made with cod fish and potato. However, today Puerto Rican chefs are reinventing the island's traditional dishes. This recipe was inspired by a shrimp and scallion ceviche that is served at Aguaviva restaurant in San Juan's trendy Sofo district. Sauteed shrimp and scallion are mixed with potato and thick veloute to make a nice batter for comforting croquetas.