1. Preheat the oven to 180 degrees, apply a little butter to the inside of the mold
2. Melt butter on low heat
3. Add the chocolate solution melted in water, mix well and let cool to room temperature
4. Beat the eggs in an egg bowl, sift the flour, and set aside with sugar and salt. Add the vanilla extract to the eggs in the egg beater, beat with an electric whisk until foamy, add sugar and continue to beat until white and viscous
5. Slowly pour the butter and chocolate liquid at room temperature into the egg liquid along the edge to avoid defoaming
6. Sift in the flour and salt, turn over from the bottom and mix well
7. Pour half of the cake liquid, sprinkle a few mulberries on top, and continue to fill the mold with cake liquid
8. Put it into the middle layer of the preheated oven, and bake at 160 degrees for about 25 minutes. Take out to cool and slice, sprinkle a little powdered sugar to decorate
