Preheat the broiler to high. On a baking sheet, toss together the olive oil, tomatillos, onion, and garlic. Transfer to the oven and broil 3-5 minutes or until charred. Remove the skins from the garlic. Add everything to a blender. Add the tomatoes and puree until smooth.
Set a large pot over medium heat. Add the tomato puree, chicken stock, chili powder, cumin, and oregano. Season with salt and pepper. Bring the broth to a boil, then reduce the heat to low and simmer 15-20 minutes.
Meanwhile, make the crema. Combine all ingredients in a food processor and pulse until smooth. Season with salt.
When ready to serve, add the chicken and hominy to the broth and cook 5 minutes or until the chicken is cooked through. Add rice to bowls, if using. Ladle the chicken and broth over the rice. Have everyone top each bowl as desired.
