Preheat the oven to 350ºF.

Place the butter in a skillet over high heat. Cook the butter until it is completely melted and aromatic, smelling caramelized, and the butter has little browned bits in it. Remove from the heat.

Break the chocolate into rough pieces by hand and add it to the butter. Stir the butter and chocolate until the chocolate has melted into the butter. Little bits of chocolate aren’t a problem. There is no need to go crazy. Let the butter and chocolate mixture cool for a few minutes.

Meanwhile, whisk the eggs and sugar together in a medium bowl until combined. Add the butter and chocolate mixture, a little bit at a time and whisking constantly, until the mixture is smooth and uniform. Mix in the cocoa powder followed by the flour. Finally, fold in the chopped walnuts.

Pour the batter into a greased 8 1/2-inch square baking dish and spread it out evenly using a rubber spatula. Sprinkle the pinch of salt over the top and bake for 30 minutes, or until a cake tester inserted in the center is mostly clean, but still comes out with some wet crumbs on it.

Once the brownies come out of the oven, let them cool briefly before placing them in the freezer until cool, about 30 to 45 minutes. After this the brownies can be stored in the refrigerator. Enjoy!