Preheat your oven to 170°c (150°c for fan-assisted ovens, Gas Mark 3 or 350°F) and grease a couple of baking sheets with a little excess butter/margarine.
Rub together the flour, sugar and butter/margarine in a large bowl until it resembles breadcrumbs.
Add the beaten egg and vanilla and mix together to form a dough.
On a floured surface, roll your dough to a few millimetres thick and cut with a cookie cutter to your desired biscuit size - around 7cm (3-inch) is ideal.
Transfer your biscuits to your pre-greased baking sheets and bake for 20 minutes until slightly golden and dry in appearance.
Allow to cool on the tray for a short while before transferring to a wire rack to cool completely.
Melt the milk chocolate in a small bowl (over a bain-marie or in short bursts in a microwave) and gently dip the bottom side of your biscuits into the chocolate - allowing the excess to drip away - before finishing with a squiggle decoration with a fork.