Pat dry the chicken thighs with paper towels. Season with salt and pepper.
In a medium cast-iron or nonstick skillet over medium-high heat, warm the olive oil. Add chicken with skin side down and cook for 12 - 13 minutes, without moving them. Check the chicken at about 8 minutes. If the skin is getting too dark, turn the heat down a little. Turn the chicken over and cook for another 10 - 12 minutes. Remove the chicken to a large plate.
In the same skillet, reduce the heat to medium-low heat. Use a couple paper towels to wipe off the fat. Add 3 tablespoons water and scrap the brown bits with a wooden spatula. Add black garlic and sauté for 1 minute. Pour in half and half, oregano and 3 more tablespoons of water. Bring to a boil. Add the cheese and stir until melted. Season with salt & pepper to your own taste. Return the chicken to the pan and cook for 4 minutes. Add spinach and cook until just wilted. Transfer chicken and spinach to serving plates. Scoop sauce over the chicken. Serve with rice or couscous.