Beat the butter with the sugar, the eggs and the lemon zest.
Gradually add the milk, the sifted flour, and the yeast.
Mix well.
Divide the dough and in two, in one of them, add the 2 two tablespoons of chocolate and mix well!
With the form greased with butter and flour, go settlers a spoonful of white mass, another of chocolate mass, until finished.
Bake for 35 minutes, depending on the power of the oven!
If you prefer, you can add cover.
Mine I put brigadier topping!