Add chocolates and cream to a large microwave safe bowl and microwave for 20 seconds at a time, mixing each time until smooth. Cover with plastic wrap and set aside to set at room temperature.
To prepare frosting add food gel to it and mix until well combined.
Preheat a fan-forced oven to 160C (320F) or 180C (356F) for a conventional oven. Line a cupcake tin with cupcake liners.
Spray the donut pan with oil spray and brush using a pastry brush. Set aside
In the bowl of a stand mixer fitted with the paddle attachment, add the flour, baking powder, caster sugar and salt. Turn mixer on low speed and allow it to mix for a couple minutes to help everything combine well (alternatively you may do this by sifting the ingredients together). Add the softened butter and let it mix until it resembles a fine sand like texture.
Next, add milk, eggs, yogurt, oil, red and pink food gel, watermelon essence and vanilla extract in a large jug and whisk well.
Add wet ingredients to dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl, add choc chips and gently fold into batter.
Add batter to a piping bag and pipe batter into donut tray filling 12 holes half way.
Fill each cupcake liner 3/4 of the way (using an ice cream scoop to transfer the batter into the cupcake liners makes this a quick and easy process otherwise you can use two tablespoons).
Bake for 20-25 min or until a toothpick inserted comes out clean. Allow them to cool completely on a wire cooling rack before frosting.
Core the centre of each cupcake and fill with green ganache.
Fit the end of a piping bag with a Wilton 6b piping tip. Frost a double donut swirl on top. Drizzle green ganache on top. Carefully place cake donut on top. Drizzle more green ganache on top and finish off with a generous helping of cotton candy right before serving.
Cupcakes can be stored in an airtight container for up to three days.