Preheat oven to 400* and line or grease muffin tins.
Combine sugar and butter in a large bowl and mix well. Beat in egg, then stir in polenta and orange zest.
Combine dry ingredients, then add 1/3 to the moist batter. Add half of the orange juice, then alternate adding dry ingredients and juice, mixing slightly. (Add more OJ if needed.)
Fold in chocolate chips.
Spoon into muffin tins.
Bake for 20 to 25 minutes, until golden and firm.