Beat the margarine, icing sugar and rice syrup using the whisk on a hand mixer, continue to beat until the mixture becomes lighter in colour. Mix the flour with all the other ingredients up to and including the baking powder, mix in carefully with the oat milk. Beat in the aquafaba using the whisk on a hand mixer, continue to beat until the mixture becomes firm. Carefully mix into the batter.
To shape the madeleines
Transfer the batter to a piping bag with a serrated nozzle (approx. 10 mm in diameter), pipe approx. 25 madeleines onto a baking tray lined with baking paper, ensuring they are well spaced out.
Approx. 10 mins. on the bottom shelf of an oven preheated to 180°C. Remove, allow to cool slightly.
Whisk together the icing sugar and oat milk. Coat the warm madeleines with the icing and leave to dry.