Is it cake? Or is it pi?

I’m happy to announce that this is my 100th post! And I’m proud that it happens to be an exceptionally nerdy one at that. Thanks for reading! 🙂

I recently had the great pleasure of having the Kumquat Fairy as my temporary roomate while she was finishing up her lab work at Berkeley. I was very sad to see her leave. (There were many an inappropriate joke about kidnapping.) In one of the last few nights she spent in Berkeley, the Kumquat Fairy brought Joe and I a couple of gifts. She made the mistake of letting me open the presents after having a fewof drinks over at my favorite Tiki bar (i.e. I was very excitable). She was very sweet and gave me Ready for Dessert: My Best Recipes by David Lebovitz and a very nerdy cake mold. A pi cake mold!


Is it cake or is it pi?

I was so bouncy at the idea of using the pi cake mold immediately, that the Kumquat Fairy indulged my slightly inebriated state and helped me make a pi cake. (Mostly to make sure I didn’t hurt myself, but you know how it is.) We flipped through the pages of Ready for Dessert and found a recipe for which we had all the ingredients on-hand. After all, it was already 11 PM, so we couldn’t very well go to the store for special ingredients! The recipe we chose is called “Banana Cake with Mocha Frosting.” The original recipe also called for salted candied peanuts, but we had a different idea for decorating.



I know what you’re thinking if you follow this blog. What is it with me and baking bananas?? Well, it’s just not my fault. Joe keeps buying these huge bunches of bananas, and we can’t get through them fast enough. *Groan* Anyway…back on task. Here’s how you can make your very own Banana Mocha Pi Cake!

Recipe card cake

Directions: Preheat the oven to 350 °F. Grease the living bananas out of that pi cake mold with butter.

Very impressive buttering, Kumquat Fairy!

Very impressive buttering, Kumquat Fairy!

We weren’t sure if this was necessary, but we cut out a π shape out of parchment paper to line the very bottom of the shape. We hoped that this would ensure the cake wouldn’t tragically stick in the pi.

I think we were both surprised at my pi-cut-out ability at this point. Go me!

I think we were both surprised at my pi-cut-out ability at this point. Go me!

Make the batter: In a small bowl, mix together the dry ingredients (flour, cinnamon, baking powder, baking soda, and salt). In another small bowl, mash your ripe bananas until smooth. In a stand mixer, beat together the butter and sugar on medium with the paddle attachment, 3-5 minutes. Add the vanilla and espresso powder. Beat in the eggs, one at a time. Mix in half of the dry ingredient mixture. Mix in the banana mash and buttermilk. Stir in the remaining dry ingredients, and fold in the nuts. Don’t overmix the batter. 

Fill the π shape first to prevent any large air bubbles. Then pile on the rest of the dough!


Time to bake the cake! The original recipe calls for 40 minutes for two 9″ pans. By the time this point in the night came, I’d already had a couple more drinks and my kitchen was starting to resemble that of Hannah Hart. (Love!) So I don’t remember how long it took. If I had to guess, I’d say 50 minutes. But, when in doubt, use a cake tester or toothpick to check for doneness. Cool in the mold on a wire rack for 10 minutes, and then carefully remove the cake by inversion onto a cake stand. Don’t let the cake cool in the mold, or it will steam itself.


Success!! Sweet, nerdy success!!

Recipe card frosting

Make the mocha frosting:  Melt the chocolate over a double boiler with the coffee, or in a heatproof bowl over a simmering  pot of water. Remove the bowl from heat once the chocolate is fully melted and smooth. Whisk in the butter until it’s fully incorporated. That’s pretty much all there is to it! Just let the frosting cool before spreading it on your lovely cake!

We wanted to decorate our little math baby with sprinkles to make the π shape really stand out. So first spread the mocha frosting onto the π. For this, I used a silicone brush.

Math is colorful too, you know!

Action shot in my nerd pjs!!

Then give the π a healthy coating of colored sprinkles. We used multicolored tiny dots for our decorating, but you could use any shape or color depending on what you’d like your final product to look like.


Lastly, we coated the remainder of the cake with the mocha frosting until completely covered. Not only was this a delicious cake, but it was a very impressive cake to bring in for a lab party we had the next day.


Here’s to nerd friends for life! Enjoy!


2 thoughts on “Is it cake? Or is it pi?

  1. Pingback: Happy Pi Day! | Heather HomeMaker

  2. I’m so happy I found this post! I ordered this mold to use for Pi Day at my son’s school and was at a complete loss on how to use/decorate the thing. (I am NOT crafty or a baker. lol)
    Thank you! Thank you! Thank you!

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