Preheat oven to 350°F (175°C).

Melt chocolate in boiling water.

Stir in vanilla and salt after chocolate is melted.

Cream shortening and sugar together until light and fluffy.

Beat in egg yolks until well combined.

Gradually add 3/4 cup of buttermilk, alternating with sifted cake flour.

Dissolve soda in the remaining 1/4 cup buttermilk.

Add buttermilk-soda mixture to the creamed mixture and mix well.

Stir in the melted chocolate mixture.

Gently fold in the beaten egg whites until just combined.

Divide batter evenly among three 9-inch cake pans.

Bake for 25 to 30 minutes, or until a wooden skewer inserted into the center comes out clean.

Let cakes cool in pans for 10 minutes before inverting onto a wire rack to cool completely.

Frost cooled cake layers with your favorite German Chocolate frosting.