Shamrock Sugar Cookies with Royal Icing

These buttery cut-out sugar cookies hold their shape perfectly and provide a smooth canvas for decorating with glossy royal icing.

The dough is easy to roll and the cookies stay soft for days under that crisp icing shell.

Why You’ll Love It

• Cookies hold their shape without spreading
• Dough rolls out smoothly without sticking
• Royal icing dries hard for easy stacking and packaging
• Recipe scales easily for large batches
• Cookies stay fresh for over a week when iced

Ingredients

For the Sugar Cookies

• 3 cups all-purpose flour
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon salt
• 1 cup unsalted butter, softened
• 1 cup granulated sugar
• 1 large egg, room temperature
• 2 teaspoons vanilla extract
• 2 tablespoons milk

For the Royal Icing

• 4 cups powdered sugar, sifted
• 3 tablespoons meringue powder
• 5-6 tablespoons warm water
• 1 teaspoon vanilla extract (use clear vanilla to keep icing white)
• Green gel food coloring

Optional Decorations

• Gold or white sprinkles
• Edible glitter
• Green sanding sugar

Steps

1. Whisk together the flour, baking powder, and salt in a medium bowl and set aside.

2. In a large bowl, beat the softened butter and sugar with a hand mixer or stand mixer on medium-high speed until light and fluffy, about 3 minutes.

3. Add the egg, vanilla extract, and milk, and beat until combined.

4. Add the flour mixture in two additions, mixing on low speed until just combined after each.

5. The dough should come together and pull away from the sides of the bowl.

6. Divide the dough in half and flatten each portion into a disk about 1 inch thick.

7. Wrap each disk tightly in plastic wrap and refrigerate for at least 1 hour or up to 3 days.

8. When ready to bake, preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

9. Remove one disk of dough from the refrigerator and let it sit for 5 minutes to soften slightly.

10. Roll the dough out on a lightly floured surface to 1/4-inch thickness, rotating and flipping occasionally to prevent sticking.

11. Cut out shapes using a shamrock cookie cutter, pressing straight down without twisting for clean edges.

12. Transfer the cut cookies to the prepared baking sheets, spacing them 1 inch apart.

13. Gather the scraps, re-roll, and cut more cookies until all dough is used.

14. Bake for 8-10 minutes, until the edges are just barely starting to turn golden.

15. The centers may look slightly underdone but will firm up as they cool.

16. Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before icing.

17. For the royal icing, combine the powdered sugar and meringue powder in a large bowl.

18. Add 5 tablespoons of warm water and the vanilla extract.

19. Beat on low speed until combined, then increase to medium-high and beat for 5-7 minutes until the icing is thick and glossy.

20. The icing should hold stiff peaks for outlining—if too thick, add water one teaspoon at a time.

21. Transfer about 1/3 of the icing to a squeeze bottle or piping bag fitted with a small round tip for outlining.

22. Thin the remaining icing with water, a teaspoon at a time, until it flows like honey—this is your flood icing.

23. Add green food coloring to both icings and mix until the color is uniform.

24. Outline each cookie with the thicker icing, then fill in with the flood icing using a squeeze bottle or spoon.

25. Use a toothpick to spread the icing to the edges and pop any air bubbles.

26. Add sprinkles or decorations while the icing is still wet.

27. Let the cookies dry completely at room temperature for at least 6-8 hours or overnight before stacking.

Helpful Tips and Substitutions

Chilling the dough is essential—warm dough spreads during baking and loses its shape.

If the dough becomes too soft while cutting, return it to the refrigerator for 10-15 minutes.

Meringue powder is available in the baking aisle and creates a stable icing that dries hard—do not substitute raw egg whites.

For pure white icing, use clear vanilla extract instead of regular.

Keep any icing you are not using covered with a damp paper towel to prevent it from drying out.

If your flood icing is too thin, it will run off the edges; if too thick, it will not spread smoothly.

A fan or dehumidifier can speed up icing drying time.

For a simpler option, skip the outline step and use medium-consistency icing that spreads but holds its shape.

Serving Ideas

Arrange decorated cookies on a platter for St. Patrick’s Day parties.

Package individually in clear cellophane bags tied with green ribbon for gifts or party favors.

Stack in a cookie gift box with parchment between layers.

Use as edible place cards by piping names onto each cookie with a contrasting icing color.

Set up a cookie decorating station and let guests ice their own cookies.

Make-Ahead and Storage

Unbaked dough disks can be refrigerated for up to 3 days or frozen for up to 3 months.

Thaw frozen dough in the refrigerator overnight before rolling.

Baked, uniced cookies can be stored in an airtight container at room temperature for up to 1 week or frozen for up to 3 months.

Once iced and completely dry, cookies can be stored in a single layer or stacked with parchment between layers for up to 10 days.

Do not refrigerate iced cookies as humidity will cause the icing to become sticky.

Royal icing can be made ahead and stored in an airtight container at room temperature for up to 2 weeks—rebeat before using.

Final Thoughts

Shamrock sugar cookies are a classic St. Patrick’s Day project that looks impressive but follows a straightforward process.

Master the icing consistency and you can decorate cookies for any holiday.

These make excellent gifts and always disappear quickly at parties.