Sift flour, baking soda and vanilla powder into a large bowl. Add in rolled oats and mix well, set aside.
Cream butter at medium till light and add light muscovado into it and beat till butter becomes white. Add by beaten egg, mix well.
Pour in the flour and rolled oats mixture, fold well with a rubber spatula to form a soft dough.
Roll dough into small balls, about 15g each and place on a lined baking tray. Lightly press down dough ball with your finger and bake at preheated oven 180 deg C for about 20 minutes till crisp.
Store biscuits in an airtight container after cooling.
Recipe by Anncoo Journal at https://www.anncoojournal.com/rolled-oats-biscuits/