Ingredients:

  • 280 g all-purpose flour, sifted
  • 8 g baking powder
  • 3 g fine salt
  • 170 g unsalted butter, softened
  • 300 g granulated sugar
  • 3 large eggs (150 g), at room temperature
  • 10 ml pure vanilla extract
  • 240 ml whole milk, at room temperature
  • 227 g unsalted butter, softened (white buttercream)
  • 480 g powdered sugar, sifted (white buttercream)
  • 30 ml whole milk (white buttercream)
  • 5 ml pure vanilla extract (white buttercream)
  • pinch of salt (white buttercream)
  • 113 g unsalted butter, softened (black buttercream)
  • 240 g powdered sugar, sifted (black buttercream)
  • 30 g Dutch-process cocoa powder (black buttercream)
  • 15 ml whole milk (black buttercream)
  • 2.5 ml pure vanilla extract (black buttercream)
  • 1 tsp (5 ml) black gel food coloring, added gradually

Instructions:

  1. Preheat the oven to 180°C (350°F). Grease two 9-inch (23 cm) round pans and line the bottoms with parchment paper.
  2. Sift the flour, baking powder, and salt into a bowl and set aside.
  3. Beat the butter and sugar on medium speed for 3 to 4 minutes, until pale and fluffy.
  4. Add the eggs one at a time, beating well after each. Mix in the vanilla.
  5. Add the flour mixture in three additions, alternating with the milk and starting and ending with flour. Mix only until the batter is smooth.
  6. Divide the batter evenly between the pans and smooth the tops.
  7. Bake for 25 to 30 minutes, until the edges are golden, the cake springs back when lightly pressed, and a toothpick inserted in the center comes out clean.
  8. Rest the layers in their pans for 10 minutes, then turn them onto a rack and cool completely, about 1 hour.
  9. Level the cooled layer tops with a serrated knife.
  10. For the white buttercream, beat 227 g softened butter on medium for 2 minutes, until creamy.
  11. Add the sifted powdered sugar gradually on low speed, then add the milk, vanilla, and pinch of salt. Beat on medium for 3 minutes, until smooth, fluffy, and free of grit.
  12. Place one cake layer on a serving board or turntable and spread about ¾ cup of white buttercream over the top.
  13. Set the second layer cut-side down on top so the surface is flat.
  14. Spread a thin crumb coat of white buttercream over the top and sides. Refrigerate for 30 minutes, until firm to the touch.
  15. Apply the remaining white buttercream as a final smooth layer over the chilled cake. Smooth the sides and top with an offset spatula.
  16. For the black buttercream, beat 113 g softened butter on medium for 1 minute.
  17. Add the powdered sugar and cocoa gradually, then add the milk and vanilla. Beat until smooth, about 2 minutes.
  18. Add the black gel a little at a time until the frosting looks deep black. Rest for 10 minutes, then check the color and add more gel if needed.
  19. Lightly sketch the pattern on the chilled white surface with a toothpick: one central pentagon on top, with a ring of pentagons and hexagons around the sides.
  20. Fill a piping bag fitted with a small round tip (#3 or #4) with black buttercream. Pipe the outline of each patch, then fill it in. Work in short, steady strokes and keep the bag cool.
  21. Let the cake rest for 15 minutes so the patches set fully.
  22. Cut into 16 slices and serve.