Preheat oven to 350°F (175°C). Grease and line two 8-inch cake pans with parchment paper.
In a large bowl, whisk together flour, cocoa powder, sugar, baking soda, baking powder, and salt.
Add eggs, buttermilk, oil, and vanilla extract. Mix on medium speed until well combined.
Gradually stir in hot water or coffee until the batter is smooth (it will be thin).
Divide the batter evenly between prepared pans and bake for 28–30 minutes, or until a toothpick inserted in the center comes out clean.
Cool cakes in the pans for 10 minutes, then transfer to wire racks to cool completely.
To make ganache, heat heavy cream in a saucepan until just simmering, then pour over chopped chocolate in a bowl. Let sit for 2 minutes, then stir until smooth.
Place one cake layer on a serving plate. Spread a thin layer of ganache on top, then arrange sliced strawberries over it.
Place the second cake layer on top, and frost the top and sides of the cake with the remaining ganache.
Chill the cake for 15–20 minutes before slicing. Garnish with whole strawberries if desired.