Preheat the Oven to 180°C (350°F) and line a 9"x13" baking dish with non stick cooking paper.
Add the egg, milk and vanilla extract and beat in.
Spread the digestive biscuits in a layer in the prepared dish.
Spoon over the cookie mixture until it has completely covered the digestive biscuit base.
Save money on Easter eggs by using more chocolate buttons than eggs.
If you don't want the marshmallow eggs to spread as mush as mine did, omit placing them on the slice until it has cooked for 12 minutes first.