In a bowl, mix 150 g plain yogurt, 1 tbsp lemon juice, 1 tbsp grated ginger, 2 minced garlic cloves, 1 tsp garam masala, 1 tsp ground cumin, 1 tsp ground coriander, 1 tsp smoked paprika, 0.5 tsp ground turmeric, 0.25 tsp cayenne pepper (if using), and 0.5 tsp salt. Add 600 g chicken thigh chunks and stir to coat. Cover and refrigerate for at least 30 minutes or up to 4 hours.