with the two packages of graham crackers, use your food processor or place in plastic bag and use your rolling pin to make crumbs. The crumbs should be fine, however, if some escape the processor it's ok to have some larger pieces. Add the sweetened condensed milk, and chocolate chips stir with wooden spoon, batter will be very stiff.
Use an 8x8 or 9x9 baking pan that has been well greased and floured. Bake 25 minutes in a 325 degree oven. Let cool and slice like brownies.