Marinate the Chicken: Combine the chicken thighs, Greek yogurt, coconut milk, garlic, ginger, sliced onion, Herbie's Garam Masala, Herbie's Yemeni Spice Mix, toasted cumin, turmeric, cayenne pepper, and tomato paste in a large resealable plastic bag. Seal tightly, squeezing out excess air, and massage to thoroughly coat the chicken. Refrigerate for at least 2–4 hours (or overnight for best flavor).
Preheat your oven to 400°F. Pour the entire contents of the plastic bag (chicken and marinade) into a small baking dish or casserole dish, spreading the chicken in an even layer.
Scatter the butter cubes evenly over the top of the chicken and marinade, then sprinkle the white sesame seeds over the top.
Cover the baking dish tightly with aluminum foil and bake for 20 minutes.
After 20 minutes, remove the foil and bake uncovered for an additional 15–20 minutes, or until the liquid bubbles down slightly, the chicken reaches an internal temperature of 165°F, and the sesame seeds/edges begin to lightly brown.
Make the Couscous: While the chicken finishes baking, bring the water (or broth), Williamson Wines Extra Virgin Olive Oil, and salt to a boil in a small saucepan. Remove from heat, stir in the couscous, cover with a lid, and let stand for 5 minutes. Fluff with a fork and fold in optional fresh herbs.
Serve: Spoon the warm couscous onto plates, top with the baked chicken and rich sauce, garnish with fresh cilantro, and serve with a chilled glass of Viognier.