Chocolate Sauerkraut Cake

Make the Cake
Adjust two oven racks to the upper-middle and lower-middle positions and heat the oven to 350 degrees. Grease and flour three 9-inch cake pans. Whisk the flour, cocoa, baking powder, baking soda, and salt in a medium bowl. Whisk the water, eggs, and vanilla in a large measuring cup.
With an electric mixer on medium-high speed, beat the butter and sugar together until fluffy, about 2 minutes, scraping down the bowl as necessary. Reduce mixer speed and ddd the flour mixture and the water mixture alternately, beating after each addition until combined. Use a rubber spatula to scrape down the bowl and stir to combine.
Using a rubber spatula, fold in the sauerkraut and pecans. Divide the batter evenly among the prepared pans and bake until a toothpick inserted in the center comes out clean, 25 to 30 minutes, rotating and switching the pan positions halfway through baking. Cool the cakes in the pans for 10 minutes then, remove from pan and peel off parchment paper. Cool completely on wire racks, at least 30 minutes.
Make the Frosting and Filling
Whisk the melted chocolate chips and mayonnaise in a medium bowl and reserve 2 cups. To the frosting remaining in the bowl, add 1/3 cup of the coconut and 1/3 cup of the chopped pecans (this is the filling).
Make the Cake
Adjust two oven racks to the upper-middle and lower-middle positions and heat the oven to 350 degrees. Grease and flour three 9-inch cake pans. Whisk the flour, cocoa, baking powder, baking soda, and salt in a medium bowl. Whisk the water, eggs, and vanilla in a large measuring cup.
With an electric mixer on medium-high speed, beat the butter and sugar together until fluffy, about 2 minutes, scraping down the bowl as necessary. Reduce mixer speed and ddd the flour mixture and the water mixture alternately, beating after each addition until combined. Use a rubber spatula to scrape down the bowl and stir to combine.
Using a rubber spatula, fold in the sauerkraut and pecans. Divide the batter evenly among the prepared pans and bake until a toothpick inserted in the center comes out clean, 25 to 30 minutes, rotating and switching the pan positions halfway through baking. Cool the cakes in the pans for 10 minutes then, remove from pan and peel off parchment paper. Cool completely on wire racks, at least 30 minutes.
Make the Frosting and Filling
Whisk the melted chocolate chips and mayonnaise in a medium bowl and reserve 2 cups. To the frosting remaining in the bowl, add 1/3 cup of the coconut and 1/3 cup of the chopped pecans (this is the filling).

Spread half the filling on one cake layer. Repeat with the second layer and the remaining filling. Top with the final layer and spread the top and sides of the cake with the reserved frosting.

Mix together the remaining coconut and pecans and toast them in a skillet over medium heat. Stir constantly until the start to turn light golden brown, then remove from heat immediately. Dump them out of the pan onto a piece of paper towel or a waiting plate to cool. Leaving them in the pan can cause them to burn, even if the pan is removed from the fire.

When topping has cooled, press it into the sides of the cake. Cover and refrigerate until ready to serve. (The cake can be refrigerated for up to 3 days.)