Set out the butter and eggs to come to room temperature.
Cream the room temperature butter and brown sugar until a smooth, thick, uniform texture develops. Use the paddle attachment on a stand mixer, which is the triangle-looking one.
With a fork, briefly beat the eggs and add them to the butter and sugar mixture in 3 increments. Mix after each addition.
Add the vanilla to the butter, sugar, eggs and beat until the mixture morphs into a smooth, thick batter that is light yellow in color and falls in clumps from a spoon.
Measure the flour and sift it into a large mixing bowl. Sift in the salt and baking powder.*
Add the dry ingredients to the butter, sugar, eggs and vanilla mixture 1/2 - 1 cup at t time. Gently stir after each addition, don't overmix. The batter will be very thick.
Add the chocolate and nuts all at once and stir to evenly distribute.
Divide the batter into two 8 x 8 metal pans. Use the butter wrappers to help spread it around evenly. Place the pans on a baking sheet and bake 30 - 35 minutes at 350. When done, the top will be a shiny golden brown, the edges will be pulling away from the sides of the pan, and a toothpick comes out clean.
While the brownies are baking, clean and dry the mixer. These brownies are iced immediately upon removal from the oven.