Preheat the oven to 180 degrees C. Combine the ground almonds, caster sugar and cornﬂour in a mixing bowl and mix well. Add the egg whites and vanilla extract and beat well to make a fairly stiff mixture.
Line two baking trays with rice paper and put teaspoons of the mixture, in round blobs, on the paper, spacing them well apart. Alternatively, put the mixture into a piping bag fitted with a large, plain nozzle and pipe onto the paper. Lightly press a split almond into the centre of each macaroon. Bake in the oven for 15–20 minutes, or until pale golden brown. Remove from the oven and leave to cool on the trays.
When cold, remove the macaroons from the trays and tear away the excess rice paper from each biscuit. (The rice paper is edible.) Store in an airtight container.