• Preheat the oven to 350 degrees and line three 6-inch cake pans with parchment paper then nonstick spray. Set aside.

Chocolate Cake

• In a medium-sized mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
• In a large bowl, whisk together the warm water, kefir, eggs, oil, and vanilla extract until combined. Add the dry ingredients into the wet and whisk together until fully combined.
• Divide the batter amongst the three prepared cake pans and bake for 23-28 minutes, or until a toothpick inserted into the middle of the cakes come out clean. Let the cakes cool in the pan for 25 minutes before removing and placing them on a wire rack to cool completely.

Oreo Buttercream

• Using a food processor, pulse the Oreos into fine crumbs. Set aside.
• In the bowl of an electric stand mixer using the paddle attachment, beat the butter on high speed until light and creamy (1-2 minutes). Add the powdered sugar, heavy whipping cream, and vanilla extract and mix on low speed until combined.
• Increase the speed to high and beat the frosting until smooth and creamy (1-2 minutes). Add the Oreo crumbs and mix on low speed just until everything is combined. Use a rubber spatula to fold in any remaining loose ingredients if needed.

Chocolate Ganache

• In a small bowl, add the chocolate chips.
• In a microwaveable-safe bowl, heat the heavy whipping cream until bubbling (30-45 seconds). Pour the heavy cream over the chocolate chips and allow it to sit for 3 minutes, then whisk together until smooth.
• Cool for 15 minutes on the counter or in the refrigerator.

Assemble

• If needed, use a serrated knife to level off the tops of each cake layer to create a flat surface. Place one cake layer on a cake stand or plate and spread about ⅔ cup of frosting. Repeat with the second layer.
• Top the cake with the last layer and spread on about ¼ cup of frosting. Frost and smooth the outside of the cake with a thin coat of frosting. Place the entire cake in the refrigerator or freezer for 10 minutes to chill.
• Pour the chocolate ganache into a piping bag or squeeze bottle and slowly drip around the border of the cake. Or to make it even easier, pour the chocolate ganache over the top of the cake, allowing it to drip down the sides.
• With the remaining buttercream I used the Wilton 1M piping tip to decorate the top of the cake. Refrigerate the cake for at least 15 minutes before serving so it's easier to cut. Keep any leftover cake slices in an airtight container in the refrigerator for up to 5 days.