Preheat oven to 350°F. Microwave chocolate chips in a microwavable bowl on MEDIUM (50%) power until melted, about 2 1/2 minutes, stirring every 30 seconds. Stir until mixture is smooth. Cool 5 minutes. 

Beat sugar and butter with a heavy-duty stand mixer fitted with a paddle attachment on medium speed until well blended, 3 to 5 minutes. Add eggs, 1 at a time, beating just until blended after each addition. Add melted chocolate, beating just until blended. 

Sift together flour, baking soda, and salt in a bowl. Add to chocolate mixture in 3 additions, alternately with buttermilk, beginning and ending with flour mixture. Beat on low speed just until blended after each addition. With mixer running on low speed, gradually add hot water in a slow, steady stream, beating just until blended. Add vanilla; beat on low until incorporated.

Grease (with shortening) and flour 3 (8-inch) round baking pans. Line bottoms with parchment paper; lightly grease. Pour batter into prepared pans. Bake in pre-heated oven until a wooden pick inserted in center comes out clean, 22 to 26 minutes. Cool in pans on wire racks 10 minutes. Remove from pans to wire racks, gently remove parchment paper, and cool completely, about 1 hour.

Place 1 cake layer on a cake stand. Top with 1 cup of the Swiss Meringue Buttercream. Spread to edges. Repeat with second cake layer and 1 cup of buttercream. Top with third cake layer. Frost top and sides of cake with remaining buttercream, using a small offset spatula to achieve a textured look. Garnish with Magnolia or Camellia Cake Toppers.