Rémoulade is the classic French cold sauce built on mayonnaise sharpened with mustard and brightened with chopped capers, cornichons, herbs and anchovy or a dash of acid. Creamy, tangy and savoury, it is the near-mandatory partner to cold seafood, fried fish and, dressed as céleri rémoulade, to raw shredded celeriac — and in Louisiana it becomes a spicier, often reddish Creole cousin heavy with mustard, paprika, garlic and hot sauce.