Place the egg whites, almond essence, icing sugar, salt and ground almonds into a food processor and blend to a smooth paste.
Dust a clean work surface with icing sugar, turn the mixture out and roll into a sausage shape. Wrap with cling film and place in the fridge for an hour.
Preheat the oven to 160C/150C Fan/Gas 3 and line two baking trays with baking paper.
When ready to bake, cut into 2cm/1in slices and roll each one into a ball. Place onto the lined baking trays about 2cm/1in apart and sprinkle a few flaked almonds over the top of each. Press gently to make the almonds stick and to squash the cookies a little.
Bake in batches for 20-25 minutes or until lightly golden.