Preheat oven to 170°C and line baking trays with non-stick parchment paper.
Sift flour, baking powder, bicarbonate of soda and salt together. Set aside. Beat butter, both sugars, essence and eggs until pale and creamy.
Put cooking oats in a food processor and pulse for a minute. Remove and combine with sifted ingredients, then stir in black currants and chocolate chips. Mix until mixture binds into a dough. Roll into small balls. Place chopped walnuts on a plate. Dip the small balls of dough into the walnuts and arrange them on prepared baking trays. Press lightly with a fork.
Bake for 15 minutes or until lightly golden. Leave the cookies on the baking tray to cool before transferring to a wire rack to cool completely. Store in airtight containers.