Preheat oven to 425°F/175°C. Lightly grease a mini muffin pan or use liners.
In a large bowl, cream together the butter, oil, sugar, and brown sugar until combined and smooth. Add the eggs and beat to combine.
Stir in the baking powder, baking soda, nutmeg, cinnamon, salt, and vanilla.
For this recipe, you will want to measure the flour by lightly spooning into the measuring cup, then leveling off. Stir in the flour alternately with the buttermilk, beginning and ending with the flour. Stir until thoroughly combined.
Spoon the batter into the prepared muffin pan, about 1 tablespoon for each mini muffin, or about 3/4 full.
Bake the mini muffins for 7-9 minutes, or until a toothpick inserted into the center of one of the middle muffins comes out clean. Do not over bake or the muffins will be dry! (If making standard size muffins in a standard pan, bake for about 15 minutes.)
Remove from oven and let cool for a few minutes. Meanwhile, in a small bowl, mix together the melted butter, powdered sugar (adding gradually), vanilla, and water. Mix until smooth.
Dip the top of each muffin into the glaze. Allow the glaze to set, then dip each a second time and allow glaze to set again. Serve and enjoy!
Notes
Works well for standard size muffins too - adjust cooking time and make half the amount of glaze.