Preheat the oven to 350 degrees F. Have a 9x13 inch baking dish out.

In a small bowl, whisk together the flour, baking soda and salt.

Place the butter in a skillet over medium heat. Cook and let the mixture bubble, stirring occasionally, until brown bits begin to appear on the bottom. Once the brown bits appear, turn the heat off and continue to stir for about 30 seconds. Let the butter cool slightly. Take a pastry brush and brush a bit of the butter all over the bottom and sides of the 9x13 inch dish.

Place the brown sugar in a large bowl. Pour in the brown butter and mix until combined and smooth - the sugar will somewhat dissolve. Add the eggs one at a time, stirring immediately after so they don’t cook if the butter is still warm. Stir in the vanilla extract.

Use a wooden spoon to stir in the dry ingredients until they are almost combined. Stir in the crushed oreos until they are evenly dispersed.

Press the mixture into the buttered dish. Bake for 25 to 30 minutes, or until the top is golden brown and set in the center. Remove the dish and sprinkle the top with flaked salt if you wish. Let cool completely before slicing into squares.