Preheat the oven to 375°F (190°C).
Place the chicken breasts in a baking dish.
In a blender, combine the tomatillos, onion, garlic, and jalapeno. Blend until smooth.
Pour the tomatillo mixture over the chicken breasts, making sure they are fully coated.
Cover the baking dish with foil and bake for 25 minutes.
Remove the foil and continue baking for an additional 5-10 minutes, or until the chicken is cooked through and the sauce has slightly thickened.
Serve the Suegra's Tomatillo Chicken with rice or tortillas.