How to Decorate Rainbow Unicorn Cookies with Buttercream Frosting

My niece turned five this month and she had a pastel rainbow unicorn birthday party. So of course, I had to make her some fun unicorn cookies.

These decorated unicorn cookies are topped with a soft vanilla buttercream frosting. So good!

And since many of the party-goers are gluten free, I made these specific cookies gluten free. I will include my regular (not gluten free) recipe in this post but if you want gluten free, here’s my gluten free sugar cookie recipe.

I’ll be teaching you how to create smooth rainbow blending with buttercream as well as the full decorating tutorials.  You will find both video and step-by-step photos of how to make the unicorn cookies.

Let’s get started!

This post may contain affiliate links to Amazon, which means I may receive a commission, at no extra cost to you, if you make a purchase through a link. Please see my full disclosure for further information.*

Part 1: Gathering the Supplies for the Buttercream Unicorn Cookies

To decorate these rainbow unicorn cookies, you will want to gather:

• 9 Icing bags
• One Wilton #2 tip, seven round tips (a mixture of tip #3, 4, and/or 5, whatever you have on hand), a star tip (such as #18), and one large round tip (such as a 10 or 12)
• 8 couplers
• Unicorn cookie cutter, unicorn horn cookie cutter, and birthday number cookie cutter
• Red, orange, yellow, green, blue, purple, and pink gel food dye (If you use this set linked, mix the red and yellow to make your own orange since orange doesn’t come in the set.)
• Palette knife (I love this one for cookies!)
• Plastic wrap
• Star sprinkles, optional
• Ingredients for a crusting buttercream & sugar cookie dough – found below in recipe card

Part 2: Baking the Cookies and Setting up the Icing Bags

Use the recipe card below for the sugar cookie and buttercream frosting recipes.

Rainbow Unicorn Cookies with Buttercream Frosting

These unicorn cookies are buttery and soft as they are topped with a vanilla buttercream frosting. Show them off as a party decoration and enjoy them as a fancy treat for a unicorn birthday.

Print Pin Rate

Course: Dessert

Cuisine: American

Keyword: Buttercream Sugar Cookies, Unicorn Cookies

Prep Time: 30 minutes minutes

Cook Time: 10 minutes minutes

Decorating Time: 3 hours hours

Total Time: 3 hours hours 40 minutes minutes

Servings: 18 cookies, depending on the size of the cookie cutter

Author: Leah Buehler

Equipment

• Stand Mixer with Paddle Attachment
• Rubber Spatula
• Measuring cups and spoons
• Medium Sized Mixing Bowl
• Lined aluminum cookie sheet parchment paper or silicone lined baking sheet
• Rolling Pin
• Cookie cutters and tools see part 1 on this post for the specific tools needed

Ingredients

Buttercream Frosting

• ½ cup room temperature unsalted butter 4 ounces
• ½ cup room temperature salted butter 4 ounces
• 4 cups powdered sugar
• 1 tbsp. vanilla extract
• 1-3 tbsp. whole milk

Sugar Cookies

• 1 cup cold salted butter cubed
• 1 cup granulated sugar
• 3 cups all purpose flour measured with the scoop & level method
• 2 tsp. baking powder
• 1 egg
• 1.5 tsp. vanilla extract

Instructions

• Remove all of the butter from the refrigerator. You will make the sugar cookies first but the butter for the frosting needs to come to room temperature before mixing.

Sugar Cookies

• Preheat the oven to 350℉ and prepare an aluminum cookie sheet by placing either parchment paper or a silicone baking mat on it.
• In a medium sized mixing bowl, combine the flour and baking powder and mix together. Set this aside.
• Cube a cup of salted butter and then, in a stand mixer with the paddle attachment, combine the cubed butter with the granulated sugar. Mix until creamed together well.
• To the stand mixer, add in the egg and vanilla extract and mix until combined.
• Slowly add in the dry ingredients in the mixing bowl to the stand mixer.
• Roll the dough out to 3/8" thick and use the cookie cutters to cut out the cookies. Place the cookies onto the prepared baking sheet and bake for 9-11 minutes or until the tops of the cookies no longer look wet. When baking the cookies, only bake 6-8 cookies at a time to leave proper space between each cookie to cook without spreading. Overcrowding the cookie sheet will cause spread.

Buttercream Frosting

• In a stand mixer with the paddle attachment, add the room temperature salted and unsalted butter and mix on high until light and fluffy.
• Mix in the powdered sugar little by little. Add in the vanilla extract and milk about halfway through adding the sugar to help the frosting come together. Start with one tablespoon of milk and work up to three if needed, depending on the consistency you want. I like to aim for a peanut butter consistency or thinner.
• Follow the directions in Part 2 for the specific way you will divide the buttercream and set up the icing bags.

How to Decorate the Unicorn Cookies

• Please refer to Part 3 of this blog post for all of the cookie decorating tutorials.

Notes

These buttercream sugar cookies are room stable for a few days on the counter. Otherwise, store in the freezer in an airtight container until ready to use, or for up to three months. You can also freeze the undecorated cookies and buttercream frosting three months in advance to decorating.

 

Make your buttercream icing according to the recipe and separate it into eight bowls:

• • • one bowl will contain a cup of frosting, keep this white/undyed
    • split the rest of the frosting up into seven equal bowls, dye one red, orange, yellow, green, blue, purple, and pink

Add each of these colors into their own icing bags with a coupler. Don’t add the tips yet, as you’ll use the large coupler opening to create the rainbow bag of frosting.

To create your rainbow icing bag, squeeze some of each color onto a piece of plastic wrap that it is about the length of an icing bag.

Make sure not to use too much, one row of each color is plenty. You want to make sure you have enough of your colors in their own icing bags to make your sugar cookies.

Roll the buttercream up with the plastic wrap into a log.

Then, add the rolled rainbow icing (still with the plastic wrap) into an icing bag with a coupler. You can then manipulate the icing so that it fills the icing bag shape.

If you’d like to see a visual of this process, please refer to my other unicorn sugar cookie post.

Part 3: Decorating the Unicorn Cookies with Buttercream Frosting

Check out the video tutorial showing the overall process for decorating the buttercream unicorn cookies then follow the step-by-step photo series tutorial below.

How to Decorate the Rainbow Number Cookies with Buttercream

1. Using a round tip such as the 3, 4, or 5, pipe a rectangle onto the number cookie at the top with the red frosting & fill it in.
2. Continue creating each rectangle of frosting with all of the colors.
3. Using your palette knife, begin to smooth the frosting. You can go over more than one frosting color at a time as long as you don’t mix the colors together. If you’re struggling, pop the cookies into the freezer for 10 minutes prior to spreading the frosting. You can add more of the colors if you accidentally wipe it off.
4. Use the palette knife to clean up the edges of the number cookies.
5. Attach a round tip to the white buttercream and outline the number cookie.

How to Decorate the Unicorn Cookies with Buttercream

1. Using a round tip on the white buttercream, outline and fill in the area of the unicorn that does not include the hair or horn.
2. Smooth the buttercream with the palette knife & clean up the edges if needed. Make sure to round out the area of the unicorn’s behind.
3. Use a round tip on your preferred color of icing to pipe a straight line for the hooves and a swirl for the unicorn horn.
4. Attach the star tip to the rainbow bag of buttercream to pipe the unicorn hair and tail. I piped small “s” shapes and connected them together for the mane. For the tail, pipe the beginning and end a bit thinner and the middle of the tail a bit wider.
5. Optionally, add a star sprinkle (or a few) to the unicorn’s hair.
6. Attach the tip #2 to the white buttercream and outline the unicorn’s body, except where the hair is.

How to Decorate the Unicorn Horn Cookies with Buttercream

1. Use the rainbow icing bag with the large round tip (10 or 12) to pipe a swirl onto the horn cookies. Try to keep the decorating tip close to the cookie to avoid large logs of buttercream.

These rainbow unicorn cookies are perfect for anyone who loves unicorns and needs a fun birthday themed cookie.

If you want to bring these cookies to a birthday party, make sure to read my post on how to package and transport buttercream sugar cookies.

Decorating for a Unicorn Birthday Party

My niece had the cutest unicorn birthday party. She had iridescent confetti stars on the table, iridescent streamers between the doorways, and, of course, rainbow unicorn horns.

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Save the Tutorial for These Unicorn Cookies

Use the image below to pin this tutorial for unicorn buttercream cookies to your birthday party board on Pinterest. Alternatively, use any of the social share icons on the top of the page to share it to your favorite social media site.