Tonkatsu sauce is a classic Japanese sauce used as a condiment to accompany tonkatsu, a Japanese culinary speciality made from breaded and fried pork. This thick, flavoursome sauce is made from ingredients such as soy sauce, rice vinegar, sugar, spices and vegetables.tonkatsu sauce offers a combination of sweet, salty and slightly tangy flavours. It adds a touch of depth and umami to every bite of tonkatsu, creating the perfect balance between the crunchy textures of the meat and the richness of the sauce. It adds a touch of depth and umami to every bite of tonkatsu, creating a perfect balance between the crunchy textures of the meat and the richness of the sauce.This versatile sauce can also be used to season other dishes such as gyozas, okonomiyaki, tempura and stews. It adds a delicious, authentic note to a variety of Japanese culinary preparations.