1) In advance, slice chicken into thin strips. Stir together with Greek yogurt, garam masala, chili powder, cumin, coriander, salt, and pepper. Cover and store in refrigerator for up to 24 hours.
2) To make sauce, add 4 tablespoons Land O Lakes® Butter to a medium pot over medium heat. Once butter has melted, add onions, ginger, and garlic and cook until veggies soften, 3-4 minutes.
3) Add tomato paste and stock to pot and stir to combine. Add prepared chicken strips along with any sauce in the bowl. Bring pot to a low simmer. Simmer mixture for 10 minutes, stirring occasionally. Test chicken for doneness.
4) Add cream to pot along with final 4 tablespoons Land O Lakes® Butter. Allow sauce to thicken for a few minutes. Taste and season with salt and pepper to your liking.
5) Serve butter chicken over rice garnished with fresh cilantro.