In a heavy-bottomed pot, heat oil. Add whole spices (fenugreek seed, fennel seeds and nigella seeds) and fry on medium heat until aromatic.
Add sliced onion and continue to fry on medium heat until evenly soft and brown, about 5-7 minutes.
Lower heat and add crushed ginger and garlic. Fry for 30 seconds to 1 minute.
Add ground spices and fry until they stop smelling raw. Deglaze the pan with a splash of water if needed.
Increase heat to high and add crushed tomatoes. Mix well and stir on high heat until the oil begins to separate from the tomato-onion base.
Add chicken and sear on high heat until no longer pink.
Add ¼ cup water and bring to simmer. Partially cover the pot and let the chicken cook for about 10 minutes.
Lower heat and add in whisked yogurt. Mix well.
Remove from heat and stir in mixed pickle if using.
