Preheat oven to 350 degrees.
Line some cookie sheets with either silicone baking mats or parchment paper.
In a large bowl, cream the butter and sugar with a mixer paddle attachment or hand mixer for two minutes. Stop and scrape the bowl. Cream the mixture for an additional minute. Beat in the egg and vanilla extract. Beat until well combined.

Sift together baking powder and flour. Add the flour mixture 1 cup at a time to the creamed butter and sugar mixture. Mix thoroughly after each addition. Blend in the last cup of flour by hand. The dough will be stiff. Divide the dough into two balls. Wrap with plastic wrap and refrigerate for at least one hour.

Roll out one ball of dough between two sheets of parchment paper to about 1/4 in. thick. Remove the top sheet of parchment paper and run a floured metal spatula under the dough to loosen it a bit. Cut cookies with cookie cutters of your choice. Dip them in flour before each use. Carefully place the cutout cookies onto prepared cookie sheets.

Cut another sheet of parchment paper and roll out dough between that and the lined bottom. Cut out cookies with cookie cutters dipped in flour before each use.
Bake cookies for 8 to 10 minutes or until they just start to brown. Let the cookies rest on the cookie sheet for 5 to 10 minutes before removing them to a cooling rack. Cool completely before glazing. Repeat process with second ball of dough.

For Glaze (if using): In a mixing bowl, thoroughly mix the sugar and the milk. The mixture should be very soft and have a heavy cream texture before you add the corn syrup. Add the corn syrup and mix just until combined. Mix in the extract and food coloring if you are planning on using only one color. If using many colors, divide up the glaze into as many bowls as you need. Color each one using gel or paste food coloring (mix in a small bit at a time using a toothpick until you get the color you want). Use a small pastry brush to glaze the cookies. Paint the entire tops of the cookies with a thin layer of glaze and place back on the cooling racks to dry. Depending on temperature and humidity, it will take between 6 and 12 hours for the glaze to dry completely.