1. Add the margarine and sugar to a large bowl and mix until very light and fluffy. Add the egg and vanilla extract and mix until well combined. Next, add the flour and salt and mix in – the dough will be very soft and sticky. Add the rainbow sprinkles and work them quickly into the dough so they have no chance of bleeding out. Divide the dough and shape each piece into a log and wrap it into plastic wrap. Place in the fridge overnight.

2. Preheat the oven to 180°C (350°F). Line a baking sheet with baking parchment and set aside.

3. Add the coarse sugar to a plate that is at least as big as one of the dough logs, and roll the first log in the sugar to cover it completely. Cut the log into (not too thin) slices and place those slices with enough space in between on the prepared baking sheet – the cookies spread a bit. Bake the cookies for about 12-14 minutes or until lightly browned around the edges. Take the cookies out of the oven and let them cool down on the baking sheet for some time, then transfer them to a wire rack and let them cool down completely. Repeat with the remaining dough.

4. If you want to decorate the cookies, melt the chocolate and dip the cookies on one side into the chocolate, sprinkle them with some more rainbow sprinkles and let them dry completely. Decorating the cookies is optional. The cookies are great with anything added on top. ;P