Christmas Sugar Cookies

Ingredients

• 3 cups all purpose flour for dough
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt
• 1 cup unsalted butter softened
• 1 cup granulated sugar
• 1 large egg
• 1 tablespoon milk
• all purpose flour for rolling out dough
• 4 cups powdered sugar plus a little more if needed
• 3 tablespoons meringue powder buy in grocery stores' baking aisle
• 7 tablespoons water room temperature, plus more if needed, for icing
• food coloring gel red, blue, green, or other favorite, for icing
• 1 teaspoon water room temperature, plus more if needed, for filling icing
• food coloring gel red, blue, green, or other favorite, for filling icing
• candy decorations candy sprinkles, sparkling or sanding sugar, cake sparkles, and/or sugar pearls, optional