Katsu curry sauce is a popular Japanese sauce that is typically served with breaded and fried chicken, pork or tofu. This flavourful sauce is rich and aromatic, with a slightly sweet and tangy taste. The main ingredients used to make katsu curry sauce include onions, carrots, garlic, ginger, tomatoes, soy sauce, and curry powder. Some variations of the sauce may also include apple, honey, or Worcestershire sauce, depending on the recipe.