Preheat oven to 180˚C. Line a 20cm round cake pan with greaseproof paper.
Place Dr. Oetker Nona Butter Cake Marble and eggs in a mixing bowl. Mix at medium speed for 3 minutes.
Add in butter and mix at low speed for 1 minute or until batter is smooth.
Divide the batter into 2 portions, add cocoa powder into one portion and mix well. Scatter a few tablespoons of the cocoa batter into the baking pan. Then pour the original batter on top. Lastly add some cocoa batter on top. Use a skewer to make a zig-zag pattern on top.
Bake at 180˚C for 55 - 60 minutes.
Melt Dr. Oetker Nona Cooking Chocolate in microwave or over a sauce pan. Pour in whipping cream, stir until well combined.
Spread chocolate sauce generously over the cake, serve with sliced strawberries.