For the Roasted Tomatillo Sauce: Preheat oven o 425 degrees. Cut the tomatillos in half and add to a sheet pan with either parchment paper or foil. Add the jalapeños. Take the garlic cloves and put in a small bit of foil, drizzle with some olive oil, salt and pepper and wrap up. Place the tin foil “ball” of garlic on the sheet pan as well. Drizzle the tomatillos and jalapeños with olive oil, salt and pepper. Toss to make sure that everything is coated. Place in preheated oven for 25 minutes. Once the tomatillos, jalapeños, and garlic are roasted – add it all (including juices) to a food processor or blender. Add the cilantro, sour cream, and chicken stock. Pulse until your mixture is smooth. Check to see if you need more salt and pepper.