By now your butter/sugar mixture will be somewhat cool. Add the egg and vanilla extract to the butter/sugar mixture and whisk until blended. Pour in the flour mixture and stir with a rubber spatula until the ingredients are just combined, then stir in chopped snickers bars, and finally the milk chocolate chips.
Drop the dough over the brownie batter in large scoops and spread it evenly with a small offset spatula.
Bake until a wooden pick or a knife inserted in the center comes out with small, gooey clumps of brownie sticking to it and the chocolate chip layer has set, about 35-40 minutes. Do not bake these brownies longer than 40 minutes or they won’t be fudgy.
Transfer the baking pan to a rack to cool completely, preferably overnight.
With a knife or a small square biscuit or cookie cutter, cut the brownies into small squares measuring about 1 inch each. If your knife or cutter has pieces of fudgy brownie stuck to it, just clean the knife and continue cutting. It helps if the brownies are completely cool, hence the overnight cooling. You can speed up the process by placing the pan in the refrigerator once the pan has cooled a bit. Once the brownies are cut, drizzle those mofos with melted Dulce de Leche and top with chopped Snickers (if desired)
Makes about 16 normal sized brownie or 32 bite sized brownie situations.