How to Make It
In a large bowl, combine the beer with the chopped rosemary sprigs, crushed garlic and vinegar and season with salt and pepper. Add the chicken and turn to evenly coat. Cover and let marinate in the refrigerator for 1 hour.
Preheat the oven to 425°. Remove the chicken from the marinade and pat dry; discard the marinade. In a large cast-iron skillet, heat the oil. Season the chicken with salt and pepper. Cook half of the chicken skin side down over moderately high heat until golden and crisp, 4 to 5 minutes. Transfer to a plate. Repeat with the remaining chicken. Return all of the chicken to the skillet skin side up and bake for 15 to 20 minutes, until browned and cooked through. Transfer to a platter.
Pour off all but 1/4 cup of the oil from the skillet. Add the chopped rosemary leaves, sliced garlic and Rice Krispies and cook over moderate heat, stirring, until the cereal is golden, about 3 minutes. Stir in the Grape-Nuts and parsley and season with salt and pepper. Sprinkle the Rice Krispies mixture on the chicken and serve.