Preheat the oven to 350°F (177°C). Line an 8-inch square baking pan with parchment paper, leaving some overhang on the sides for easy removal later.
Add graham crackers to a food processor and process until they’re very finely crushed crumbs.
Add chocolate chips to a large microwave-safe bowl. Heat in the microwave at full power in 30 second increments, stirring in between with a spatula, until the chocolate is completely smooth and melted.
Add in the condensed milk and mix until the batter is uniform in color.
Stir in the crushed graham crackers until they are evenly combined. Finally, fold in the chopped walnuts. The batter will be very thick but do your best to stir until evenly combined.
Pour batter into the prepared baking pan. Use a spatula to even out the surface if needed.
Bake for about 30 to 35 minutes until a toothpick inserted in the center comes out clean. Let brownies cool completely before cutting. Because of how fudgy the brownies are, I recommend using a large sharp knife and heating the blade by dipping it into hot water before cutting (wiping the blade clean after each cut).
