For the Chicken Marinade:

• 1.5 lbs boneless, skinless chicken thighs, cut into 1-inch cubes
• 1/2 cup full-fat plain Greek yogurt
• 1 tbsp lemon juice
• 1 tsp ground turmeric
• 1 tsp garam masala
• 1/2 tsp ground cumin
• 1 tsp salt

For the Sauce:

• 3 tbsp unsalted butter, divided
• 1 tbsp neutral oil
• 1 large yellow onion, finely chopped
• 1 tbsp minced fresh ginger
• 3 cloves garlic, minced
• 1 tsp ground cumin
• 1 tsp ground coriander
• 2 tsp garam masala
• 1 (24 oz) jar tomato passata
• 1/2 cup heavy cream
• 1 tsp sugar (optional)
• Salt to taste
• Fresh cilantro, for garnish