Preheat the oven to 350 degrees F. Spray mini muffin pans with baking spray.
For the cupcakes: Mix together the flour, cornmeal, baking powder, baking soda, and salt in a large bowl until combined; set aside.
Whip together the butter and sugar in a standing mixer with the paddle attachment on high speed until it becomes light and fluffy, about 6 to 8 minutes. Beat in 1 egg at a time until well blended; add in the milk and sour cream. Beat in the dry ingredients on low speed until completely mixed in.
Bake for 20 to 25 minutes or until they are lightly browned and firm in the center. Cool to room temperature.
For the butter cream: Whip the butter in a standing mixer with the paddle attachment on high speed until light and fluffy. Add in the powdered sugar and maple syrup on low speed until combined and then whip it on high speed for 2 to 3 more minutes. Frost cooled cupcakes with the butter cream and serve.