Preheat your fan oven to 160°C (325°F) or 175°C (350°F) if you’re not using a fan oven. Line your cupcake/muffin pan with paper cases.
In a medium sized bowl sift and combine flour, cocoa powder, baking powder, sugar and salt. Set aside.
In another medium size bowl beat aquafaba using a whisk for a minute, until it becomes white and frothy. Add oil, rice milk, vanilla extract and red food coloring (start small, then add more if necessary) and mix until it all combines. These are your wet ingredients.
Add your wet ingredients to the dry ones in two batches. Mix everything until just combined.
In a small jug, combine together baking soda and vinegar. A reaction will occur producing bubbles. In that exact moment, add that mixture to the batter and mix everything thoroughly. The batter will be on the runny side.
Divide the batter evenly among the paper cases, filling them ⅔ of the way full. Bake for 20-25 minutes or until they're springy on the top. Once they're done, let them cool completely before frosting.
For frosting:
In a small saucepan combine flour, sugar, salt and rice milk. Cook over medium-high heat, stirring constantly with a whisk until it thickens.
Once it’s done, transfer it to a bowl, put a cling film over it touching the surface to prevent “skin” forming and let it cool to room temperature. This is your pudding base. You can do this in a fridge, but before using it let it come to room temperature.
Using a stand mixer fitted with the paddle attachment, beat the vegan butter for 5 minutes until it’s pale and fluffy. Then add spoonful by spoonful of previously made pudding. Mix until it’s all nicely incorporated and with no lumps. Add vanilla extract and mix until everything is combined.
Assembly:
Put the buttercream in a piping bag fitted with 2D tip (or whichever you prefer ? ) and frost the cupcakes. They are best eaten at room temperature. You can keep them in an airtight container at room temperature for 2 days or longer in the fridge. Just let them come to room temperature before eating them. Fridge makes cakes and cupcakes drier so bear that in mind.
Notes
You can use a hand mixer if you don't have a stand mixer.
If you still don't own one, I advise you to buy a kitchen scale - they're cheap and easy to use, and always guarantee the same results in baking!
Not all ovens are the same. I suggest checking the cupcakes at 20 minute mark and then adjust the baking time accordingly. Get to know your oven!
Make sure not to overfill your paper cases, otherwise the batter will "explode".
You can use some other plant-based milk substitute, I just find that the rice one has the most neutral, sweet flavour.
If you're using powder food coloring you'll need less than if you're using gel! I don' recommend water based food coloring - it's not strong enough and can alter the consistency of the batter.