Toast mustard seeds and fenugreek seeds in a dry pan over medium heat until fragrant. Grind them into a fine powder and set aside.
In a large bowl, combine the ground seed powder, red chili powder, turmeric, garam masala, minced garlic, grated ginger, and salt. Add yogurt and mix to form a marinade.
Add chicken thighs to the marinade and coat well. Refrigerate for at least 1 hour or overnight for best results.
Heat vegetable oil in a large pan over medium heat. Add marinated chicken and cook for 5 minutes on each side until browned.
Pour in water, cover, and simmer for 20 minutes until chicken is fully cooked and tender. Stir in lemon juice before serving.
Notes
Serve hot with basmati rice or naan for a complete meal. Adjust chili powder according to your spice preference.