Dry roast red chillies, garlic, ginger, mustard seeds, fenugreek seeds and turmeric powder and grind along with vinegar to a smooth paste.
Add salt and mix. Heat oil in a non-stick pan, add the ground paste and cook for five to seven minutes.
Add the chicken pieces and cook on low heat for eight to ten minutes or till the chicken is cooked.
Remove from heat and set aside to cool.
Spoon into a clean dry jar and let it stand for two-three days before using.