For the Cookies:

1. In a stand mixer fitted with the paddle attachment, beat the butter and Caster Sugar until light and fluffy - about 3 minutes. Scrape down the sides of the bowl as needed. Add the egg and vanilla. Beat on high until fully combined - about 2 minutes. Scrape bowl as needed.
2. In a medium mixing bowl, whisk the flour, baking powder and salt together. Turn the mixer down to low and add 1/2 the flour mixture, beating until just combined. Add the remaining 1/2 of the flour mixture and continue mixing until just combined. If dough is too soft, add a 1 tsp of flour at a time until it's the desired consistency.
3. Roll dough onto a piece of parchment to about 1/4" thickness. Place on a baking tray and chill for 2-3 hours in the refrigerator. Don't skip this step or cookies will spread!
4. Once dough is chilled, heat oven to 350. Line 2-3 large baking sheets with parchment paper or a silicone mat. Remove dough from fridge and using a cookie cutter, cut into shapes. Place cut cookies onto prepared baking sheets. Re-roll extra dough and continue cutting until all is used.
5. Bake for 9-12 minutes, or until the edges of cookies are a light golden brown.  Allow cookies to cool for about 5 minutes and then transfer to a cooling rack.  Allow cookies to cool completely before icing.

For The Royal Icing:

1. In a stand mixer fitted with the paddle attachment, beat together the Fondant and Icing Sugar, vanilla and milk. It should be thick. If too thick, add 1/2 Tbs milk. If it is too thin, add an additional Tbs of sugar. I like to get the icing to a consistency where if you drizzle a bit with a spoon, the ribbon  will hold for a few seconds before melting back into the icing. If desired, divide icing into separate bowls and add coloring options of your choice.
2. Decorate cookies however you'd like. I like to use squeeze bottles for the royal icing. Cookies will stay soft for about 5 days at room temperature.