Classic Vanilla Sugar Cookies with Royal Icing

1. Combine Dry Ingredients

In a large bowl, whisk together the flour, baking soda, cream of tartar, and salt. Set aside.

2. Cream Butter and Sugar

Using an electric mixer, cream the butter and confectioners' sugar until light and fluffy. Mix in the vanilla extract, then the egg.

3. Form Dough

Gradually add the flour mixture, beating until just combined. Divide the dough in half, shape into flat rectangles, wrap in plastic, and refrigerate for at least 2 hours.

4. Roll Out Dough

Remove one dough half from the refrigerator. Roll out to 1/8-inch thickness between two sheets of parchment or plastic wrap. Repeat with the remaining dough. Chill rolled-out dough for 20 minutes.

5. Preheat Oven and Cut Shapes

Set the oven to 350°F (175°C). Prepare four cookie sheets with parchment paper, lightly floured if necessary. Cut out cookie shapes from the chilled dough, placing them 1 inch apart on the prepared sheets. Bake until golden at the edges, about 8 to 13 minutes. Cool on a wire rack.

6. Make Icing

In the mixer, whip together the confectioners' sugar, egg whites, cream of tartar, and a pinch of salt until stiff and glossy.

7. Tint Frosting and Decorate

If using colors, divide the icing into bowls, covering unused portions. Stir in food coloring as desired. Make two consistencies for each color: thick for outlines and thin for flooding. Fill piping bags with icing and use small round tips to pipe onto cooled cookies. Let icing set for at least 2 hours before serving.