Line a baking form with a baking paper.
Melt the chocolate in a saucepan or in the microwave, stir many times during the melting time.
Add the condensed milk and vanilla extract and stir together. Be aware the batter will be very thick.
Pour and spread the mixture in the baking form, flatten a bit with a spoon.
Place in the fridge for 2 hours.
Take it out and cut in small squares.