Sift the flour and salt into a mixing bowl. Add the sugar, Trex, unbeaten eggs, milk and vanilla extract. Use a wooden spoon to beat the mixture together until smooth and creamy – this will only take 1-2 minutes.
Spoon the mixture into the paper cases. Bake for 10-12 minutes, until risen and golden. Cool in the tin for a few minutes, then transfer to a wire rack to cool completely.
When the buns are completely cool, slice the tops from them and cut these in half. Spoon a little jam into each bun, then share the butter icing between them. Replace the tops to resemble wings, then sift a little icing sugar over the buns.