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Preheat oven to 350 degrees F. Grease and line 3 8-inch round cake pans with parchment paper. Use Baker's Joy or lightly flour bottom and sides of pan.
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Melt chocolate in microwave-safe bowl for 40 seconds, then stir. Continue heating in 15 second increments until fully melted. Set aside to cool.
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In a medium bowl, combine flour, baking soda, and salt. Whisk to combine and set aside.
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Using the paddle attachment on your electric mixer, cream butter and brown sugar until smooth (1-2 minutes). Add eggs and beat until well combined.
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Add vanilla extract and melted chocolate, and beat until well combined.
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Add flour alternately with sour cream, beating until just combined.
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Add boiling water, and stir with a spoon until blended (batter will be very thin).
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Pour into prepared pans and bake for 18-22 minutes, or until cake pulls away from the sides of the pan and a toothpick in the center comes out clean. Remove from oven and let cool in pans for 10 minutes. Remove to cooling rack to cool completely.
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Clean an 8 inch cake pan and line with saran wrap or foil. Place a layer of chocolate cake in prepared pan, then gently spread 2 8 ounce containers of cookie dough on top to cover completely. Gently pull out layer using saran wrap or foil and place on cake platter or stand. Repeat with a second layer and place on top of the first, then add third cake layer to the top.