Preheat oven to 180 degrees. Line a 12 hole muffin pan. I used 7 big muffin cups.
Beat butter and sugar till fluffy. Add the egg one at a time and beat at each addition.
Sift in the flour and fold the mixture.
Add the rest of the ingredients and fold till completely well folded. Do not over beat.
Divide equally between the muffin pans. Bake for 25 to 35 minutes, till a skewer inserted comes out clean.
Cool on a rack completely before spreading a little of the frosting on each muffin.
For frosting, simply whisk together the ingredients till combined. Plop onto each muffin. Enjoy with a cup of coffee... These muffins taste even better the next day!