Preheat oven to 375F.
In a large bowl, whisk flour, cornmeal, baking powder, and sugar until evenly combined.
In a medium bowl, whisk butter, egg, milk, and miso. Combine with flour mixture and mix until all is combined.
Pour into a muffin pan and bake for 15-20 minutes.
Cream butter and miso with an electric mixer until fully combined.
Serve on muffins while still hot.