• Whisk the dry ingredients together in a bowl and set aside.
• Cream the butter, sugar, and vanilla together, scraping down the bowl to get everything combined. Blend in the egg.
• Fold the dry ingredients into the wet to form a soft pliable dough.
• While the dough is soft, roll it out to 1/4-1/3 inch thick. You can do this on a large sheet of parchment paper, with another sheet on top of the dough to prevent sticking. I found the top sheet unecessary, as a little dusting of flour worked fine.
• Slice the parchment paper and dough onto a baking sheet and refrigerate for 30 minutes.
• Preheat the oven to 350°F. Line 2 baking sheets with parchment paper.
• Remove the cookie dough from the fridge and cut into rounds with a 2 1/2 inch cookie cutter. Place 2 inches apart on your cookie sheets and bake for 12-14 minutes. They will still be pale, but just starting to turn golden around the edges.
• Cool the cookies on a rack until completely cooled before dipping.

marbled icing

• Blend together the sugar, milk, water, and vanilla to make a smooth runny icing. You can do this in a food processor, or by hand. Divide the icing into 2 bowls and cover with plastic wrap. Let sit while the cookies cool, this will allow the bubbles to surface.
• When the cookies are completely cooled, I suggest testing the consistency of your icing by dipping one cookie headfirst into the glaze, then flipping it over to set back on the rack. If the consistency seems fine** drop or drizzle a bit of each color across the surface of the white icing. Take a toothpick or chopstick and gently swirl the colors together. Be careful not to swirl too much, or the colors will blend and get muddy.
• Dip each cookie headfirst into the marbled icing, lift straight up, and give it a twist to set it upright on the rack. As the colors get too muddy in your first bowl of icing, move on to the next.
• Let the icing dry completely before serving or storing the cookies.