• In medium bowl, combine cocoa with boiling water, mixing with wire whisk until smooth. Cool completely. Sift flour with soda, salt, and baking powder. Preheat oven to 350°F. Grease well and lightly flour three 9 x 1 1/2-inch layer-cake pans.
• In large bowl of electric mixer, at high speed, beat butter, sugar, eggs, and vanilla, scraping bowl occasionally, until light--about 5 minutes. At low speed, beat in flour mixture (in fourths), alternately with cocoa mixture (in thirds), beginning and ending with flour mixture. Do not overbeat. Divide evenly into pans; smooth top. Bake 25 to 30 minutes, or until surface springs back when gently pressed with fingertip. Cool in pans 10 minutes. Carefully loosen sides with spatula; remove from pans; cool on racks.

Frosting

• In medium saucepan, combine chocolate chips, cream, butter; stir over medium heat until smooth. Remove from heat. With whisk, blend in 2 1/2 cups powdered sugar.  In bowl set over ice, beat until it holds shape.

Filling

• Whip cream with sugar and vanilla; refrigerate. 

To Assemble Cake

• On plate, place a layer, top side down; spread with half of cream filling. Place second layer, top side down; spread with rest of cream filling. Place third layer, top side up. To frost: With spatula, frost sides first, covering whipped cream; use rest of frosting on top, swirling decoratively. Refrigerate at least 1 hour before serving. To cut, use a thin-edged sharp knife; slice with a sawing motion.