In a bowl, mix the butter, sugar and vanilla seeds. Mix until the sugar melts, then add the whole egg, then the yolk.
Mix the flour with the baking powder and gradually incorporate it into the butter composition. Mix until you get a fairly thick dough. Cover with cling film and refrigerate for an hour.
After it has cooled, take out the dough and knead it a little. We form thin "rolls" 1 cm thick and about 20 cm long. We cut bars of approx. 7 cm.
We take a tray provided with baking paper, place the cookies and put them in the hot oven, over medium heat, for about 10 minutes. They must remain light in color, but they must be ripe. We take them out and leave them to cool on a grill.
Melt the chocolate on a steam bath, add the milk. Stir until smooth. Decorate the chocolate cookies at the ends or according to your preferences.