This Sumikko Gurashi birthday cake was requested by my daughter Isabelle for her 11th birthday. I didn’t plan on making this a post, so there aren’t a variety of in-progress shots or even final photos, alas. But hopefully the photos here show the final result clearly enough: a five-tier cake in a rainbow of pastel hues, topped with cookie cutouts of the beloved Sumikko Gurashi characters.
For those unfamiliar with these cute little critters (consisting of a polar bear, penguin, cat, dinosaur, and…a crumb of tonkatsu??), they are a set of characters by Japanese company San-X. On my recent trip to Japan, I saw these characters on merchandise everywhere from handbags to stationery to plushies. Sumikko Gurashi is also Isabelle’s current obsession, so I’m not surprised she came back from Japan requesting this theme for her birthday cake.
I was inspired by the soft pastel hues of Sumikko Gurashi to do a rainbow layer cake in pastels. The cake is Isabelle’s favorite vanilla cake, made via reverse creaming method. My recipe makes five 6-inch round layers, which is a pretty tall cake, as you can see. You can definitely adjust the recipe to make fewer 8-inch or 9-inch round layers, as you desire. I typically use gel paste food coloring in my baking – either Americolor or Chefmaster work about equally well for me, and often comes down to which one has the color I’m looking for at my local baking shop.
If you’re not frosting the sides of the cake like I didn’t, it’s important to ensure that the sides of the cake layers are as straight as possible (don’t use cake pans with sloped sides) and don’t brown too much or the cake won’t have the rainbow appearance you’re looking for. I tried using cake strips on my cake pans for the first time and I was pleased with how well worked. You may need to add a few minutes to the baking time as the strips do keep the cake batter from baking as quickly, but it’s worth it for clean, even layers that are perfectly flat and uniformly colored.
For the Sumikko Gurashi cookies, I found these adorable cookie cutters that were exactly what I needed. Success with these types of cutters relies on having a good cookie dough, and I used my cookie stamp recipe which produces a tender, shortbread-like cookies that also holds its shape and any impressions stamped onto its surface well.
It still helps to be gentle with this dough: don’t overwork the dough to avoid having tough cookies. Roll out the dough to about 1/4″ thick – any thinner and the dough may spread out more when baking and not hold its shape as well. I like to roll out the dough between two sheets of parchment paper, so if it starts getting a little soft, it’s easy to place on a baking sheet and pop in the fridge to chill. If the dough seems at all soft or sticky, like the cookie cutters are sticking to it or the cut cookies are not releasing easily from the parchment, just chill the dough for a bit – it’s always better than fighting the dough. If you also work with the dough in small batches at a time, you can leave the rest of the dough in the fridge to stay chilled.
Once the cookies are baked and cooled, I decorated them with royal icing and piped melted chocolate – fortunately the Sumikko characters aren’t too complex! Good enough to satisfy Isabelle – she declared this her favorite birthday cake yet, so I’ll take that! The cookies are also perfect as party favors. Hope this Sumikko Gurashi brings a bit of colorful cheer to your day.
Sumikko Gurashi Rainbow Cake
Ingredients
Stamped Cookies
- 2 2/3 cups (300 g) all-purpose flour
- 2 tbsp cornstarch
- 1 cup (200 g) sugar
- 1/2 tsp salt
- 8 oz (113 g) unsalted butter room temperature, cut into 1-in pieces
- 1 large egg
- 1 tbsp vanilla extract
- 1 tsp almond extract
Vanilla Layer Cake
- 2 3/4 cups (380 g) cake flour
- 1 3/4 cups (380 g) sugar
- 1 tbsp + 1 tsp (18 g) baking powder
- 1 1/8 tsp salt
- 7 oz (200 g) unsalted butter room temperature
- 5 large egg whites room temperature
- 1 large egg room temperature
- 1 1/2 cups (366 g) whole milk
- 2 tsp vanilla extract
Swiss Meringue Buttercream
- 1 1/4 cups sugar
- 5 large egg whites
- 15 oz (425 g) unsalted butter room temperature, cut into 1-in pieces
- 1 1/2 tsp vanilla extract
- 1 1/2 tsp almond extract
Instructions
For the cookies
- Combine the flour, cornstarch, sugar, and salt in the bowl of a stand mixer fitted with the paddle attachment. Mix until combined.
- Add in the butter and beat until incorporated and the mixture looks like rough crumbs. It doesn't have to come together into a ball yet.
- Add in the egg and beat until the mixture starts to come together.
- Add in the vanilla and almond extracts and beat to combine.
- Divide dough into portions and color with food coloring as desired, if you want different colored cookies.
- Flatten dough into about 1/4" thick and wrap well in plastic wrap. Refrigerate for about 1 hour.
- Preheat oven to 350 degrees F.
- Roll out the dough to about ¼" thickness. Because this dough can become soft and sticky quickly, my favorite method is to roll out between two sheets of parchment paper.
- Dip cookie stamps into a bowl of flour to lightly coat, and then press into the dough to make designs. If at any point the dough has become too soft, place back in the refrigerator for 10 minutes or more until it firms up again.
- Place cookies on baking sheets lined with silicone baking mats or parchment paper.
- Bake for 9-11 minutes until edges are light brown. Remove and let cool on wire rack.
- Decorate cooled cookies as desired.
For the cake
- Preheat oven to 350 degrees F. Grease and flour five 6" round cake pans. Line the bottoms with parchment paper.
- Combine cake flour, sugar, baking powder, and salt in a stand mixer fitted with the paddle attachment.
- Add the butter and beat until a crumbly mixture forms, just starting to come together.
- Add the egg whites one at a time, and beat to combine. Add the egg and beat to combine.
- Combine milk and vanilla extract together in a measuring cup. Add to the mixer in three additions, beating well after each addition.
- If you want to be precise, weigh the batter so you know divide evenly between the five pans.
- Pour one-fifth of the batter into one of the prepared pans. Add food coloring as desired.
- Pour another fifth of the batter into a second pan. Continue adding more food coloring as desired and pouring batter into the pans.
- Bake for about 24-28 minutes, rotating halfway. The cakes should be set and a skewer inserted in the center should come out with a few crumbs on it.
- Remove and place on wire racks. Run a knife around the edges for easier removal. Let cool for about 20 minutes and then invert pans to remove cakes. Let them finish cooling before decorating.
For the buttercream
- Combine the sugar and egg whites in a medium metal bowl and place over a pan of simmering water.
- Whisk the sugar mixture constantly over heat until the sugar is dissolved and the mixture looks smooth and shiny.
- Continue whisking until the mixture reaches 160 degrees F.
- Remove mixture from heat and pour into a stand mixer bowl. Whisk on medium speed for about 5 minutes until the mixture has cooled.
- Switch to the paddle attachment and with the speed on low, add the butter a few pieces at a time, beating until smooth. Do not add the butter too quickly or beat too quickly or the buttercream may break.
- When all the butter has been added, beat the buttercream on medium-high speed for about 6-10 minutes until it is very thick and smooth. It may appear to separate briefly but continue beating and it should come back together.
- Add in the vanilla and almond extracts and beat to combine.
- The buttercream is ready to be used. Place a piece of plastic wrap against the surface until you are ready to use it to prevent it from drying out.
To assemble the cake
- Level off cake layers if necessary. Place one cake layer on a cake board or cake decorating stand.
- Spread some of the buttercream over the cake layer evenly. Place a second cake layer on top and spread some more buttercream over the cake layer. Repeat with the remaining cake layers.
- Refrigerate for about an hour to let the frosting set.
Anita Chu, also known as pastrygirl, is a baker, writer, and photographer with a passion for pastry. She trained at Tante Marie's Cooking School and is the author of Field Guide to Cookies, Field Guide to Candy, and Lollipop Love. Anita lives in San Francisco with her husband, daughter, and dog Max. 
Leave a Reply