Marinate the chicken with the ingredients for chicken for at least 1.
To prepare sauce, saute onions in lard until softened. Add remaining sauce ingredients and simmer until peppers are tender. Allow mixture to cool and puree in batches in a food processor. If necessary, add water to yield 1 quart total. Set aside.
Grill chicken over hot coals until cooked through. Serve with warmed sauce spooned over. Freeze any remaining sauce (it's good for chicken again, or also enchiladas, etc.).