Slow Cooker Butter Chicken

Bahan-bahan (6 porsi)

• 3 tablespoons butter
• 1 large onion (diced)
• 5 cloves garlic (minced)
• 1 tablespoon minced fresh ginger (or ½ teaspoon ground ginger)
• 1 tablespoon garam masala
• 1 teaspoon ground coriander
• ½ teaspoon turmeric
• 1 teaspoon cumin
• 1 teaspoon chili powder
• 14 ounces crushed tomatoes
• 2 tablespoons tomato paste
• ½ teaspoon lemon zest
• 1 ½ cups heavy whipping cream (divided)
• 2 tablespoons cornstarch
• 3 pounds boneless skinless chicken thighs
• ⅓ cup chopped fresh cilantro
• ½ teaspoon salt (or to taste)