When ready to bake, preheat oven to 350˚F. Remove cookies from refrigerator and bake for 12-16 minutes or until just beginning to turn golden at the edges. Rotate pans halfway through for even browning. Cool completely before icing.
Combine powdered sugar, half and half and ¼ teaspoon peppermint extract in a medium-size bowl. Mix until smooth. The glaze should be thick but pourable. Add a little more half and half if too thick. Taste the glaze and add more peppermint extract, if needed (see note above in the post). Dip the tip of a small knife into the blue food coloring and swirl some of it into the icing. Stir well and add more food color until desired shade of blue is achieved. Transfer the glaze to a shallow bowl.
Place buttercream in a pastry bag fitted with a small round icing tip (I used a Wilton #5 round tip). Starting at the upper edge of one cookie, pipe the Christmas trees by making lines that are increasingly wider, stopping about ¼-inch above the lower edge of the cookie (see pictures above). Immediately sprinkle trees with a few more white nonpareils. Set aside to dry.
See Café Tips above for lots of extra tips and instructions. The recipe makes 15 large (3-inch) or two dozen smaller (2-inch) cookies.
The recipe makes 15 large (3-inch) or two dozen smaller (2-inch) cookies.
Once cookies have been dried for several hours, they can be stacked in an airtight container.