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1
Position rack in lower third of oven- Heat to 350 degrees.
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2
Grease a 13x9x2 inch baking pan with solid shortening- Dust with flour, tap out excess and line bottom with parchment or wax paper.
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3
Sift flour onto wax paper.
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4
Measure 2 cups by lightly spooning flour into a measuring cup (the nested kind), mounding it slightly (don't tap cup on countertop)- Sweep off excess flour with back of knife, put into a medium bowl, whisk in baking soda and salt.
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5
In a medium bowl, whisk 1/2 cup lukewarm water into the cocoa- Let cool.
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6
Pour buttermilk, 1/2 cup water and vanilla into a liquid cup measure.
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7
Crack eggs into a small bowl; whisk to mix yolks with whites.
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8
Beat butter in a large bowl with mixer on medium speed 30 to 45 seconds until smooth.
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9
On low speed, gradually beat in granulated sugar then brown sugar- Scrape down sides of bowl (mixture will appear sandy).
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10
Beat on medium speed 6 to 7 minutes until mixture is light in color and comes together.
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11
Gradually add eggs and beat, scraping bowl at least once, until fluffy and increased in volume (This, including adding eggs, should take about 1 minutes).
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12
Add cocoa mixture; beat just to blend.
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13
With a rubber spatula, stir in 1/4 the flour mixture, then 1/3 the buttermilk mixture- Repeat, alternating dry and liquid ingredients, ending with flour mixture and mixing until blended and smooth.
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14
Pour into prepared pan- Spread from center out, creating a slightly raised ridge around rim.
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15
Bake 30 to 40 minutes or until top springs back slightly when touched lightly in center, sides contract and a wooden pick inserted in center comes out clean- Cool on wire rack 10 minutes.
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16
Prepare frosting while waiting: Stir in 1/2 cup sugar and 1/4 cup unsweetened cocoa powder in a large bowl to blend.
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17
Add 1 cup heavy whipping cream; stir to combine.
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18
Refrigerate at least 30 minutes for sugar and cocoa to dissolve.
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19
Beat with mixer on high speed until stiff peaks form when beaters are lifted- Use immediately (makes 2 cups).
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20
Once the cake has cooled on a wire rack for 10 minutes, run a thin knife around edge of cake, place a wire rack over pan and flip both over- Remove pan and paper.
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21
Turn paper sticky side up, place non-sticky side on cake, cover with a rack and flip both over so cake is right side up- Cool completely.
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22
To assemble: Place cake in freezer 15 minutes.
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23
Using a serrated knife, slightly trim narrow ends.
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24
Cut cake crosswise in thirds.
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25
Place 1 third on a platter; spread with 1/3 the Cocoa Whipped Cream- Repeat with another third.
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26
Top with remaining layer; spread top with remaining cream.
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27
Refrigerate at least 30 minutes or until ready to serve.
