Preheat the oven to 350°F. Grease two 8-inch round cake pans with butter or nonstick spray.

In a large bowl, whisk together the eggs, sugar, melted coconut oil, milk, orange juice, and vanilla until smooth.

Add the flour, cocoa powder, orange zest, baking soda, baking powder, and salt. Stir gently until about 90% combined. The batter will be thick.

Pour the hot water over the batter and gently whisk until fully incorporated and smooth, scraping the bottom to remove any lumps.

Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes, until a toothpick inserted in the center comes out clean. Cool the cakes in the pans for 10 minutes, then turn out onto a wire rack to cool completely. Once cool, refrigerate the layers for 30 minutes to make frosting easier.

For the icing: In a stand mixer or with a hand mixer, beat the softened butter and salt on medium-high until light and fluffy, about 2 minutes. Gradually add the powdered sugar, 1/2 cup at a time, alternating with the orange juice and zest, beating well after each addition. Adjust the amount of powdered sugar to reach a spreadable consistency. Gently fold in the shaved chocolate by hand; do not overmix to avoid discoloring the frosting.

To assemble: If the cake layers have domed tops, level them with a serrated knife. Place one layer on a cake stand or turntable. Spread about 1/3 of the icing evenly over the top. Place the second layer on top and spread another 1/3 of the icing over it. Use the remaining icing to cover the sides. Smooth the top and sides with a cake scraper or offset spatula. The chocolate shavings will create a textured finish.

Garnish with fresh orange slices or twists if desired. Slice with a sharp knife and serve.