Preheat the oven to 180°C (160°C Fan, Gas Mark 4). Line a large baking tray with baking parchment. Make up the Egg White Powder as directed on the packet, then whisk until thick and foamy but not too stiff or dry. Mix in the Almond Extract and liqueur or orange juice.
Put the ground almonds in a bowl and sift 115g (4oz) icing sugar on top and make a well in the centre. Scrape the egg white mixture into the centre using a spatula and carefully mix together to make a stiff dough.
Divide the mixture into 16 pieces and roll each into a ball. Place on the prepared baking tray, spaced a little apart. Bake for about 15 minutes, until the biscuits are lightly golden and cracked on top. Cool for 5 minutes before transferring to a wire rack to cool completely.
To serve, dust with the remaining icing sugar and serve. For gifting, wrap the biscuits individually in small squares of tissue paper, twisting the ends to close and seal. The biscuits will store unwrapped in an airtight container for up to 2 weeks.