Moss Cake with Woodland Grapefruit Buttercream

Adapted from: The Wondersmith

Yield: 12–16 servings (one 9" cake)

Moss Cake


  • 1 12-ounce bag (340g) frozen spinach
  • ¾ cup (170g) water
  • 4 cups (480g) all-purpose flour
  • 4 tsp baking powder
  • 1 ½ cups (339g) unsalted butter, room temperature
  • 1 ½ cups (297g) granulated sugar
  • 6 eggs
  • 2 tsp vanilla extract
  • 4 Tbsp lemon juice
  • zest of two lemons
  • 1 tsp salt


  1. Heat oven to 325°F. Grease and flour two 9" (23cm) round cake pans and one other (6–9" or 15–23cm) cake pan.
    NOTE: The third cake will be crumbled, which is why the size doesn't matter.
  2. Place frozen spinach and water into blender and blitz until you have a very smooth purée. (You should end up with 2 cups of purée.) Set aside.
  3. In a large bowl, sift the flour and baking powder together. Set aside.
  4. In the bowl of a stand mixer fitted with paddle attachment, cream butter and sugar on medium until light and fluffy.
  5. Add eggs one at a time, mixing until thoroughly combined. Mix in vanilla, lemon juice, lemon zest, and salt.
  6. Starting and ending with the flour mixture, add dry ingredients and spinach purée to butter mixture alternately. With mixer on low speed, mix until combined, being careful not to overmix. Scrape down bowl as necessary after each addition.
  7. Divide the batter between the cake pans, smoothing the surface with an offset spatula or the back of a spoon. (There will be roughly 675g of batter in each pan.)
  8. Bake for 25–27 minutes. Cake layers are done when a wooden pick inserted in the centres comes out clean.
  9. Transfer to wire racks and leave cake layers in pans for 10 minutes. Then gently turn out onto wire racks to cool completely.

Woodland Grapefruit French Buttercream


  • 10 large egg yolks
  • 1 cup (198g) granulated sugar
  • 6 Tbsp (85g) water
  • 2 cups (454g) unsalted butter
  • 3 Tbsp Portland Bitters Project Woodland Bitters
  • zest of one grapefruit
  • ½ tsp kosher salt


  1. Once the cake layers are totally cool, it’s frosting time! First, in the bowl of a stand mixer fitted with whisk attachment, beat egg yolks until they are thick and foamy.
  2. While eggs are being whisked, combine sugar and water in a medium saucepan. While stirring, heat on low until sugar dissolves. Then increase heat to medium-high and bring mixture to a boil.
  3. Cook sugar mixture until it reaches 240°F (soft-ball stage). Upon reaching soft-ball stage, remove saucepan from heat immediately.
  4. With mixer on low, slowly pour hot sugar syrup into bowl with egg yolks.
  5. Keep mixing until entire bowl is cool to the touch and the yolk and sugar mixture is room temperature.
  6. Add butter to bowl one cube at a time, allowing each piece to be fully incorporated before adding the next cube.
  7. Add bitters, grapefruit zest, and salt. Keep mixing until buttercream is smooth and creamy (5–6 minutes).

Assembly & Decoration

Additional Components:


  1. With a long, serrated knife, level your two cake layers if necessary and/or desired.
  2. Put a small blob of frosting in the middle of your cake board (or serving platter) to help keep the cake in place. Then lay down one layer.
  3. Spread frosting across top of layer, then carefully place second layer on top.
  4. Using an offset spatula, spread a crumb coat over the top and sides of cake.
  5. Place cake in fridge to chill for 15–30 minutes. If it’s warm where you live, put your buttercream in the fridge as well. (Living in Atlanta, we speak from experience!)
  6. While cake is chillin’, crumble the extra cake layer into tiny pieces for the ‘moss’ coating.
  7. Remove cake from fridge, then using an offset spatula, frost entire cake with buttercream.
    NOTE: If your buttercream stiffened up a bit too much in the fridge, beat with mixer for 5 minutes before frosting cake.
  8. To catch any runaway moss, place cake on top of rimmed baking sheet. Gently press moss crumbs into frosting on top and sides of cake. (We found it easiest to give the entire cake a once-over, then go back and fill in any gaps.)
  9. Decorate with meringue mushrooms and chocolate rocks.
    NOTE: Since the entire cake is coated in moss crumbs, we recommend gently poking toothpicks straight into the mushroom stems and then attaching ‘em to the cake.

Did you try this recipe? Tag @fikabrodbox or #fikabrödbox!