Vegan Dark Chocolate Cake

To prepare cake: Preheat oven to 375 degrees F. Coat three 8-inch round cake pans with cooking spray. Line the bottoms with parchment paper and coat the paper with cooking spray.

Combine flaxseed (or chia seeds) with 9 tablespoons water in a small bowl; set aside.

Meanwhile, combine the remaining 3/4 cup water, chocolate and espresso in a small saucepan. Heat over medium heat, stirring, until the chocolate is melted. Let cool for 5 minutes.

Combine brown sugar and oil in the bowl of a stand mixer fitted with a whisk attachment. Beat until combined. Add the flaxseed (or chia) mixture and beat until smooth, about 1 minute. Stir in the melted chocolate mixture. Switch to the paddle attachment.

Sift all-purpose flour, whole-wheat flour, cocoa, baking powder, baking soda, cinnamon and salt into a medium bowl. Mix milk, vanilla and orange zest in a small bowl. Add the flour mixture to the chocolate mixture, alternating with the milk mixture, and beat until well blended. Divide the batter evenly among the prepared pans. Tap them lightly on the counter to remove any air bubbles.

Bake until the cake is just coming away from the sides of the pans, 18 to 20 minutes. Let cool in the pans for 5 minutes before turning out onto a wire rack. Remove the parchment and let cool completely, about 45 minutes.

To prepare frosting: Combine granulated sugar and water in a small saucepan. Cook over medium-low heat, whisking, until the sugar has dissolved to form a simple syrup. Attach a candy thermometer to the pan with the tip in the liquid but not touching the bottom. Increase heat to medium and bring to a lively simmer. Cook until the syrup reaches 235 degrees F.

Meanwhile, place 1/2 cup of the chickpea liquid (aquafaba) in a clean bowl of a stand mixer fitted with a whisk attachment. (Reserve the chickpeas for another use.) Beat on low speed.

When the syrup reaches 235 degrees, increase the mixer speed to high and beat the aquafaba until very stiff peaks form, at the same time continuing to cook the syrup until it reaches 248 degrees. Carefully pour the syrup slowly into the stiff aquafaba with the mixer on high speed and beat until the mixture is as thick as marshmallow fluff. Switch to the paddle attachment and beat on high speed until the outside of the bowl is cool to the touch, about 5 minutes. Add butter, a spoonful at a time, until it's completely incorporated. (If the mixture starts to look curdled, don't panic! It will come back together as it mixes.) Add vanilla and beat on medium-low speed, scraping the sides occasionally, until the frosting is thick and glossy.

To assemble cake: Place one cake layer on a serving plate. Using an offset spatula, spread 1 cup frosting on the first layer. Top with another layer and another 1 cup frosting. Top with the third layer and frost the top with 1 cup frosting. Frost the sides with the remaining 1 cup frosting.