Cream the margarine, icing sugar and vanilla extract together in a large mixing bowl.
Mix in the finely chopped dates and chocolate chips. Add in the flour and a pinch of salt and mix with your hand until it forms a soft dough.
Make the dough into a rectangular shaped block (about 8cm x 16cm x 3.5cm), wrap in cling film and let it sit in the freezer for 30-40 minutes. The dough will be hard on the outside that makes it easier to cut into slices without distorting the shape too much.
Preheat the oven to 180°C (gas mark 4.5). Prepare a baking tray with baking paper.
Cut the half frozen dough into slices (about 8mm thickness). I made 20 slices but this varies depending on the shape of your dough. Sometimes the chocolate chips pop out as you cut. Gently push it back and reshape the cookie with your hand if needed.
Place the cookies on the prepared baking tray and bake for 18-20 minutes. Let them cool down completely before coating the corners.