Preheat oven to 375ºF.

Place melted butter and shortening into an electric mixer bowl with sugar and extract and mix until smooth.

With the mixer running on low, add eggs one at a time, allowing each to mix in before adding another.

Add the first two cups of flour one at a time, scraping down after each addition, the slat and baking powder and then adding 1/4 cup flour at a time, adding just enough that dough can be rolled into a ball (it will still be sticky).

Roll dough into balls the size of a grape tomato (I don't recommend trying to measure the dough with spoons when it is this sticky- just pinch off a bit with your fingers) and place balls on a silpat lined cookie sheet or ungreased baking sheet (if you prefer) and bake about 10 minutes, or until bottoms are lightly colored but tops are still pale.

Cool cookies completely on silpat or remove to a wire rack if using ungreased sheets.

Mix glaze together and spoon lightly over the tops of the cookies and decorate with nonpareils or sprinkles as desired.