1. Prepare the Pans and Oven:

For the cake: Preheat the oven to 350°F (175°C).

Spray two 8-inch round baking pans with nonstick baking spray with flour. (Alternatively, butter and flour the pans).

2. Combine Dry Ingredients (Cake): Whisk together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking soda, baking powder, and kosher salt in a large bowl.

3. Combine Wet Ingredients (Cake):

Whisk together the eggs, vanilla extract, whole milk, and vegetable oil in a medium bowl.

4. Combine Wet and Dry Ingredients: Add the egg mixture to the flour mixture.

Whisk well to combine. Scrape down the sides and bottom of the bowl to be sure all the ingredients get mixed together and there are no clumps of batter.

5. Add Hot Water:

Add the hot (not boiling) water to the batter.

Whisk well to combine. The batter will be thin and soupy; this is normal.

6. Bake the Cake Layers:

Pour the batter evenly into the prepared pans.

Bake for 30 to 35 minutes, or until a wooden pick inserted in the center of each cake layer comes out clean.

7. Cool the Cake Layers: Cool the cakes in the pans for 10 minutes.

Then, carefully remove the cakes from the pans and transfer them to a wire rack to cool completely, about 1 ½ hours.

8. Make the Coconut-Pecan Filling:

While the cakes are cooling, make the filling.

Combine the granulated sugar, light brown sugar, evaporated milk, melted unsalted butter, egg yolks, and kosher salt in a medium saucepan.

Whisk until smooth.

Cook over medium heat, whisking frequently, until the mixture just begins to boil and coats the back of a spoon, 10 to 12 minutes.

Remove from the heat. Stir in 1 cup of the sweetened flaked coconut, the ⅔ cup of chopped pecans, and the vanilla extract.

Transfer the filling to a bowl. Cover and refrigerate until completely cooled.

9. Make the Chocolate Buttercream:

Whisk together the granulated sugar and egg whites in the heatproof bowl of a stand mixer.

Place the bowl over a saucepan of simmering water (make sure the bottom of the bowl doesn’t touch the water). This creates a double boiler.

Cook, whisking occasionally, until an instant-read thermometer registers 120°F to 130°F (49-54°C), or until the egg whites are foamy and there are no sugar granules remaining in the mixture when you rub it between your fingers.

Carefully place the bowl onto the stand mixer fitted with the whisk attachment.

Beat at medium-high speed until stiff peaks form and the bowl is cool to the touch, 7 to 8 minutes.

Reduce the speed to medium-low. Add the softened, cubed butter, a few tablespoons at a time, beating until combined after each addition. (If the buttercream breaks or looks curdled at any point, continue beating for 2 to 3 minutes, and it should come back together.)

Beat in the vanilla extract and kosher salt.

Reduce the speed to medium-low. Beat in the sifted cocoa powder until fully combined.

10. Assemble the Cake: Place about ½ cup of the chocolate buttercream in a piping bag. Cut a 1-inch-wide opening at the tip.

Pipe a ring of buttercream on top of one cooled cake layer, right along the edge. This will act like a barrier to keep the filling from squishing out the sides. (Don’t worry if you don’t use all the buttercream in your piping bag on the ring; any leftovers can be used to frost the sides).

Spread half of the cooled coconut-pecan filling on top of the cake layer, inside the buttercream ring.

Place the second cake layer upside down on top of the filling. This creates a flat top for easier frosting.

Spread the remaining coconut-pecan filling on top of the second cake layer, leaving about ½-inch around the sides for the frosting.

11. Frost and Decorate:

Spread the remaining chocolate buttercream around the sides of the cake.

Place pecan halves around the top of the cake, if desired.

Press the additional ½ cup of sweetened flaked coconut onto the sides of the cake, if desired.

12. Chill and Serve: Refrigerate or store the cake in a cool place until ready to serve.

Enjoy your beautiful and delicious German Chocolate Cake!