In a bowl beat butter and brown sugar until creamy.
Add vanilla extract and milk and mix until smooth.
Stir in heat-treated flour and mini chocolate chips to form cookie dough.
Scoop small portions of dough and flatten them slightly.
Place a small spoon of Nutella in the center of each portion.
Wrap the dough around the Nutella and roll into balls.
Chill the balls in the refrigerator for 30 minutes.
Dip each truffle into melted chocolate and place on parchment paper.
Refrigerate until the chocolate coating sets.