Combine first 5 ingredients in a small bowl; stir well. Cover and chill at least 1 hour.
Combine masa harina, baking powder, salt, and chili powder; stir well. Combine milk, club soda, egg, and egg white; add mixture to dry ingredients, stirring well. Stir in jalapeno pepper.
Dip chicken pieces in batter, coating well. Pour oil to depth of 2 inches in a Dutch oven; heat to 375°. Fry chicken, a few pieces at a time, 4 to 5 minutes or until golden. Drain on paper towels. Serve with sour cream mixture.