Place the chicken pieces in a medium bowl and add the garlic, yogurt, 1 tablespoon of the curry powder, 1 ½ teaspoons of the salt, the paprika, ¼ teaspoon of the cayenne, and mix thoroughly so that the chicken is evenly coated with the spice mixture. Refrigerate for at least 1 hour and up to overnight.

Preheat a sous vide water bath to 65 degrees C.

Heat a large nonstick skillet over medium high heat and add the oil. When hot, add half of the chicken pieces and cook until nicely browned on both sides, 2 to 3 minutes. Transfer to a bowl and repeat with the remaining chicken.

Add the butter to the hot skillet along with the shallots and ginger and cook, stirring, until softened, 3 to 4 minutes. Add the remaining tablespoon of garlic along with the turmeric, the remaining tablespoon of curry powder, remaining ½ teaspoon salt, cumin, coriander, remaining ¼ teaspoon cayenne, and black pepper and cook until spices are toasted and very fragrant, 1 to 2 minutes. Add the tomato sauce, brown sugar and cook, stirring, until the sauce thickens, 2 to 3 minutes. Remove from the heat and stir in the remaining 1 cup of yogurt. Add the sauce to the chicken and stir to combine. Spoon the chicken and sauce mixture into a gallon size resealable freezer storage bag and seal using the water displacement method.

Lower the bag into the water bath and cook for 1 ½ to 2 hours, until the chicken is very tender.

Remove from the water bath, adjust the seasoning if necessary, and serve over basmati rice or alongside naan bread, garnished with the cilantro.