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Combine cocoa and hot coffee together, stirring until smooth; add in oil and stir; set aside.
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Beat butter with a standing mixer or hand mixer until creamy and fluffy, about 2-3 minutes. Gradually add in white and brown sugar, beating about 3 minutes until it is light and fluffy. Add eggs, 1 at a time, beating just until the yellow disappears.
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Add in chocolate/coffee mixture, and beat until just combined.
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In a bowl, sift together flour, baking soda, baking powder, salt, and espresso powder.
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Stir together buttermilk, vanilla extract, and sour cream (or Greek yogurt).
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Alternately mix the buttermilk mixture and flour mixture with the butter batter, beginning and ending with the flour mixture. Do not overmix--stir until everything is just combined.
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Fill two cake pans about 1/4 of the way full with the chocolate batter. Place 7 Oreos (14 all together) in each of the two cake pans, evenly spread apart (I did 6 in a circle, and 1 in the middle). Divide the remaining batter between the two cake pans. Tap the cake pans to remove any air bubbles.
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Bake for 25-30 minutes, or until a cake tester comes out clean.