Grind the chocolate cookies in a food processor until completely ground and set aside.
Grind the walnuts until minced.
Put the ground cookies, walnuts and dulce de leche in a bowl. Mix with your hands until obtaining a smooth dough.
Make a roll about 8 inches long and refrigerate for about 10 minutes, until firm.
Melt the chocolate in a bain-marie and coat the entire chocolate roll using a brush.
Refrigerate again for 15 minutes.
Serve the roll with strawberries, raspberries, and blueberries.