In a microwave-safe container add white chocolate, water, oil, and sugar; mix well
Microwave until the chocolate melts
Add vanilla extract and mix well. Let the mixture cool down
Preheat the oven to 350 degrees Fahrenheit
Line the baking tray with parchment paper and grease it with cooking spray
In a wide bowl add all-purpose flour, baking soda, baking powder, and salt; mix well
After the chocolate mixtures turn warm add it to the dry ingredients
Add sour cream and mix everything well to make a lump free smooth batter
Divide the batter between to two cake tins, level and tap the batter
Bake for 25 – 30 minutes or until a toothpick inserted comes out clean
Flip the cake on the cooling tray and remove the pan and parchment paper
Allow the cake to cool completely
After the cake is cool, trim the top layer of the cake with a sharp knife
Cover the cake with cling wrap and refrigerate for at least 3 hours or until used