Preheat oven to 425°F (218°C). Line or grease a 12-count muffin tray.
In a bowl, whisk cornmeal, flour, baking powder, baking soda, and salt.
In another bowl, whisk melted butter, oil, brown sugar, and honey. Add the egg, then the buttermilk.
Pour the wet mixture into the dry mixture and whisk until just combined.
Fold in optional add-ins if using.
Fill muffin cups to the top.
Bake at 425°F (218°C) for 5 minutes, then reduce to 350°F (177°C) and bake 16–17 minutes more.
Cool for 5 minutes before transferring to a wire rack.