For milkmaid cookies, place the unopened! Simmer condensed milk can in a pot half-filled with water for about 1 hour. Let the can cool down!
Make a smooth dough with the flour, salt, butter, sugar, cocoa and yolks. Chill the dough for 1/2 hour. Preheat the oven to 160 degrees convection.
Line the baking sheets with baking paper. Roll out the dough to a thickness of about 3 mm and cut out round cookies. Add an opening (heart, star, etc.) to half of the cookies.
Bake the cookies for about 10 – 12 minutes. Beat the cooled condensed milk mixture well with a mixer.
To finish the milkmaid cookies, fill one cookie without an opening and one with an opening with the cream.