Chicken achari draws its tangy, bold flavor from pickling spices like mustard seeds, fenugreek, and nigella. This high protein chicken dish is naturally zesty and complements a healthy, calorie-conscious meal plan.
Combine yogurt, ginger, garlic, half the salt, and turmeric in a bowl. Add chicken thighs, toss to coat, and marinate at least 30 minutes (up to overnight) in the refrigerator.
Heat vegetable oil in a large skillet over medium-high heat. Add mustard seeds, fenugreek, nigella, and fennel seeds. Cook, stirring constantly, until the seeds begin to pop and become fragrant (about 45 seconds).
Add chopped onions to the skillet. Lower heat to medium and sauté onions until golden brown, about 7–8 minutes, stirring to prevent burning.
Stir in tomatoes, red chili powder, cumin, and remaining salt. Cook, occasionally mashing the tomatoes with your spatula, until soft and oil begins to separate, about 5 minutes.
Add the marinated chicken with all its marinade to the skillet. Increase heat to medium-high; mix well so chicken is evenly coated in the spice mixture.
Reduce heat to medium-low. Cover and cook for 15–18 minutes, stirring occasionally, until chicken is cooked through and the sauce thickens. Remove the lid to allow excess moisture to evaporate during the last 3–4 minutes for a thicker consistency.
Taste and adjust salt if needed. Serve hot with extra yogurt or lemon wedges if desired.