For the Strawberry Reduction: Puree approximately 5-6 strawberries in a blender. Pour 1/2 cup of this puree into a small saucepan and simmer on low-medium heat for about 15 minutes until reduced to 1/4 cup. Stir frequently and let cool.
Preheat the oven to 350°F (175°C), then grease and flour three 8-inch round pans.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt for 30 seconds. Set aside.
In another bowl, mix the buttermilk, oil, and vanilla.
In a mixer, blend the butter until smooth. Gradually add the sugar and mix until light and fluffy. Add the eggs one at a time, mixing well after each addition.
Slowly alternate adding the flour mixture and the buttermilk mixture, starting and ending with the dry ingredients.
Divide the batter into three bowls. To one, add cocoa powder mixed with hot water for the chocolate batter. To another, add the strawberry reduction for the strawberry batter. Leave the third bowl as vanilla.
Pour each flavor of batter into the prepared pans. Bake for 25-30 minutes or until a toothpick comes out clean. Let them cool for 10 minutes before removing from pans.
For the frosting, chill the mixing bowl and beaters. Whip the heavy cream with powdered sugar and vanilla until stiff peaks form.
In another bowl, beat the softened butter until smooth. Gradually add half of the confectioners’ sugar and most of the milk. Mix well, then add the remaining sugar and milk. Beat until smooth.
For the ganache, melt chocolate with heavy cream in the microwave, stirring until smooth.
Layer the cakes starting with chocolate, followed by a buttercream dam, whipped cream filling, vanilla layer, then another dam, and finally strawberry.
Crumb coat the cake, chill, and frost with the remaining buttercream. Decorate with ganache and chocolate chips if desired.
Notes
Use room temperature ingredients for better mixing. Adjust sweetness of frosting with salt. Thin frosting with more milk if too thick.