Heated the oven to 180C degrees. In a large pot put kuvertura chocolate, cut into prachentsa and the butter - room temperature and cut into pieces - and put in the microwave for 2 seconds on the highest power. To the melted butter add the sugar and mix well with a spatula, then add the eggs and vanilla. Then add flour, shaping the homogeneous mixture. In a rectangular pan (20x20 cm) covered with kitchen paper to cover the countries on a platter, pour the dough and bake in the oven for 30-35 minutes. Leave to cool and then cut the pieces.