Preheat your oven to 160'C fan or 180'C conventional
Mix your ground flax with the water and allow to sit for 5 minutes to thicken
Mix your oil, sugar and vanilla together, either with a whisk or a paddle attachment on a mixer
In a separate bowl, mix your flour, salt and baking powder
Add your flax mix to your oil and sugar mix once flax has thickened and continue to whisk
Add half your milk, and whisk
Sieve in half of your flour mix, and fold the batter
Add your remaining milk, followed by the remaining flour, and continue to fold until all incorporated
Bake cupcakes for 17-20 mins
Check that a tooth pick comes our clean, if not continue to bake for an additional 2 minutes.
Mix your buttercream ingredients together and pop in the fridge for 15 minutes! Decorate once the cake has fully cooled.