Cut the chicken breast into 3 pieces and fry them in a saucepan with oil until they are golden brown all over. Then stand on its side.
Heat the rest of the oil and then add the onions, garlic, ginger, chilli, mushrooms, curry paste, spices and sesame seeds to the saucepan and simmer for about 3 to 4 minutes over low heat while stirring. Then add the chicken stock, coconut milk and tomatoes. Season with salt and bring to the boil briefly. Reduce the temperature, add the chicken breast and cook with the lid open over low heat for about 10 minutes until the meat is tender and the sauce thickens.