Einkorn Yellow Cake with Chocolate Frosting

1. Preheat the oven to 375°F. Lightly butter the bottom and sides of a 9-inch round cake pan. Place a round piece of parchment paper on the bottom then butter and flour the parchment.
2. In a medium bowl, sift together the flour, baking powder, and salt.
3. In a medium bowl, whisk together the buttermilk (yogurt or milk), vanilla, and butter.
4. In the bowl of a standing mixer fitted with a wire whip, beat two whole eggs, one egg yolk, and sugar on high speed for 2 minutes until thick and pale yellow. Sift in half the flour mixture and using a spatula, fold in the flour until it is almost completely absorbed then fold in half the milk mixture. Repeat with the remaining flour and milk mixture until all the flour is absorbed.
5. Pour the batter into the prepared pan and bake for 25 to 28 minutes until the tip of a toothpick inserted in the center comes out clean.  
6. Let the cake cool in the pan on a wire rack for 30 minutes. Invert the cake onto the rack, lift off the pan and slowly remove the parchment paper. Let the cake cool completely for 1 hour more before frosting. 

Make the frosting

1. In a medium bowl, mix together the sugar, flour, and cocoa. In a medium saucepan, warm the milk on low heat. Whisk in the sugar mixture and cook for 4 to 5 minutes, over a medium-low heat, whisking frequently, until it becomes the consistency of a thick pudding. ( If you are doubling the frosting recipe, you will have to cook for 10 minutes until thick).
2. Pour the mixture through a sieve to remove any lumps, pressing the sieve with the back of a spoon. Scrape the bottom to ensure all of the mixture is added to the bowl. Place the mixture in the refrigerator to cool completely.  To cool quicker, set the bowl in a larger bowl filled with ice for 5 minutes before refrigerating.
3. Place the chocolate in a medium heatproof bowl, over a saucepan of simmering water. Stir frequently until the mixture is melted. Set aside.
4. In the bowl of a standing mixer fitted with a wire whip, beat the butter on medium for 1 minute until fluffy. Add the salt and vanilla and beat to combine.
5. Add the refrigerated mixture to the butter mixture and beat for 1 minute until combined and fluffy.
6. Add the melted chocolate and whip until completely combined and fluffy.

Assemble the cake

1. Slice the cake in half horizontally with a long serrated knife. Place the bottom layer on a rack over a baking tray. Spread ¾ cup of frosting evenly over the bottom layer with an offset spatula.  Place the second layer on top. Spread the frosting around the sides and top of the cake then smooth with a spatula.  Add a decorative rope pattern around the edges of the cake with a pastry tip, if desired.
2. This cake can be stored at room temperature for 1 day or refrigerated up to 3 days in an airtight container.

This recipe is enough to make a single layer cake with frosting. If you would like to make a double layer cake as we did, you will need two cakes and a double batch of frosting. You may make the frosting the day before, but it will harden completely in the refrigerator. To soften, let the frosting sit at room temperature for 3 hours. You should also whip the frosting in the standing mixer, fitted with the wire whip, until it is soft and fluffy again.