In a small mixing bowl, take whole wheat flour, all purpose flour, sugar, baking powder, cocoa powder and combine well.
Add milk, vanilla extract, coconut oil and whisk with a fork till smooth.
Pour into a microwave safe mug.
Make a well in the centre and press white chocolate chips and top it with peanut butter. Gently press down and level the top of the batter till the peanut butter is covered with the cake batter.
Microwave at high for 1 minute. Rest another 1/2 min in the microwave itself. Do not take it out immediately else, the cake will sink in the middle.
Serve warm with some chocolate sauce drizzled on top.