• Place flour, sugar, vanilla sugar, and egg in the bowl of a food processor. Process until the mixture is the texture of a coarse meal.
• Add the butter to the food processor. Process just until a dough forms. If the dough is too sticky, then add a spoonful of flour. If it is too dry, then add a spoonful of water.
• Flatten the dough into a disc and put it in a plastic bag. Refrigerate until chilled, about 1-2 hours.
• Preheat the oven to 320°F/160°C.
• Line two sheet pans with parchment paper.
• On a floured surface, roll out the dough to about a ½-inch (1 cm) thickness (relatively thick so that they do not break).
• Cut out as many cookies as possible and place them on prepared sheet pans. *If you choose to decorate with only sprinkles or colored sugar, do it before the cookies go into the oven.
• Bake for approximately 10-12 minutes, until golden at the bottom.
• Let cookies cool completely, preferably on a cooling rack.
• Once the cookies have cooled, you can move on to icing and decorating them!

*Optional* chocolate coating:

• In a small microwavable bowl, microwave chocolate and oil in 30 seconds intervals until melted and smooth. Dip half of each cooled cookie into melted chocolate. Decorate with sprinkles and place on waxed/parchment paper until the chocolate is set.

*Optional* sugar frosting:

• Whisk milk, powdered sugar, and a few drops of food coloring in a medium-sized bowl until it’s a thick consistency. Then, using a teaspoon or a piping bag, frost the cookies and add some sprinkles if desired. Let the cookies sit for an hour at room temperature until the frosting dries and forms a thin crust.
• Using a teaspoon or a piping bag, frost the cookies and add some sprinkles if desired. Let the cookies sit for an hour at room temperature (until the frosting dries and forms a thin crust).
• Serve them right away, or store them in airtight containers.