1) To make the cookies: Beat together the oil, butter, eggs, vanilla, Fiori, salt, baking powder, and sugar until smooth.
2) Add the flour, mixing until smooth.
3) Divide the dough in half, shape into disks, wrap in plastic, and refrigerate for at least 1 hour.
4) Preheat the oven to 350°F.
5) Roll the dough 1/8" thick on a lightly floured work surface or a silicone rolling mat.
6) Cut out 2" circles and transfer them to greased or parchment-lined baking sheets, leaving about 1" between them.
7) Using a 1/2" pastry tip, cut out a center circle from each cookie. Re-roll and cut the remaining dough.
8) Bake the cookies for 10 to 12 minutes, until their bottoms and edges have turned slightly golden; they won?t brown very much.
9) Remove the cookies from the oven, and transfer them to a rack to cool completely before icing.
10) To make the icing: Combine all of the ingredients except the nonpareils until smooth. Dip the top of each cookie into the icing, and sprinkle with nonpareils. Allow the icing to set before serving or storing the cookies.
Yield: about 50 cookies.