Begin by preheating your oven to 350 degrees Fahrenheit.
In a mixing bowl, cream the melted butter and sugar together first, then mix in the eggs and combine.
In a separate bowl, mix the flour, cocoa powder, baking powder, and salt.
Grandully add the dry ingredients into the wet ingrediante and mix until incorperated.
Stir in any add-ins like the nuts if you desire.
Pour the batter into a greased 9 x 13 baking dish and bake for 18-25 minutes or until a toothpick comes out clean.
After they have cooled off, you can top with powdered sugar if you like.
Store in an air-tight container for up to 4 days at room temperature, or in the refrigerator for up to a week.