Preheat oven to 180°C. Grease oven trays (if not non-stick); line with baking paper.
Beat butter, extract, sugars and egg in a small bowl with an electric mixer until light and fluffy. Transfer mixture to a large bowl; stir in sifted flour and soda, in two batches.
Stir in chocolate.
Spoon tablespoons of mixture roughly into balls; place 5cm apart on trays (dough will expand and spread a lot)..
Bake cookies 12-15 minutes or until golden; cool on trays.
Cookies will keep in an airtight container for up to 1 week.(if they last that long!)