Preheat the oven to 170c. Prepare muffins pan with liners, set aside.
In a large bowl, sift flour, cornstarch, powdered sugar, baking powder, baking soda, salt and whisk to combine. Add in milk, vanilla, coconut oil, white vinegar. And until well combined. Divide batter evenly between 8 cupcake lines in a muffin pan. Bake for 20 mins until toothpick comes out clean. Let cool completely before frosting.
Scrape out the cream from the canned coconut whipping cream. Stir the melted white chocolate and coconut whipping cream, folding them together. Keep stirring until combined. Cover with plastic wrap and refrigerate until solid. 2-4 hours or overnight.
Combine butter and about 1 cup of white chocolate whip cream mixture in the stand mixer bowl with the paddle attachment. Whip on medium to high speed for about 2-3 minutes.
Stop mixer and add the sifted powdered sugar. Mix on low speed until incorporated, scrape the bottom and sides of the bowl and then mix on high speed until smooth.
Note* Add more powdered sugar if frosting is too thin or another tablespoon of coconut cream if frosting is too thick.