Beat the butter and sugar with an electric mixer until pale and fluffy. Add the vanilla extract and eggs one a time, mixing with each addition.

In a separate bowl, combine the flour, baking soda and salt. Add this to the batter in 2 additions, alternating with the sour cream.

Divide the batter between 4 bowls. Keep one bowl white and dye the remaining bowls pale, medium and dark blue. Pour the batter into 4 greased and floured 8-inch round cake pans. Bake at 350F for 20 minutes, or until a skewer inserted into the cakes comes out clean. Cool in the pans for 10 minutes, then transfer to a wire rack and cool completely.

Beat the butter with an electric mixer until pale and fluffy. Add the vanilla extract and beat until combined. Add the confectioner’s sugar one cup at a time, then beat for 3-5 minutes, until fluffy.

Using a plate as a guide, trim off the edges of all cakes – this will make them look pretty when they are being stacked. Also remove any excess browning from the tops and bottoms of the cakes.

Stack the cakes, starting with the dark blue cake and transitioning to the white cake, spreading a generous amount of buttercream between each layer. Spread the buttercream right to the edges of the cakes. Then spread a thin layer of buttercream on top of the cake.

Holding an offset spatula vertically against the surface of the cake, rotate the cake to smooth the buttercream filling.

Sprinkle some brown sugar on top of the cake to look like sand. Press some brown sugar into a shot glass, then turn out onto the top of the cake.

Pour some melted white candy melts into a seashell chocolate mold and place in the freezer until set, about 20 minutes. Unmold and decorate the cake.

Enjoy!