Pre-heat the oven on 170 C.

Place the margarine in the oven for a few seconds until it's slightly soft but not melted.

In a large bowl whisk together flour, cornstarch, baking soda and salt.

In a small bowl using a mixer combine sugar and margarine, then add milk and vanilla and mix again.

Add the sugar mix to the big bowl and combine well.

Cut chocolate bar into small bits and add them to the dough.

Using a spoon form 9 flat cookies on a baking sheet with parchment paper.

Bake the cookies for around 20 min, they should still be somewhat soft.