Line an 8" baking pan with parchment paper or foil. Spray the paper or foil with cooking spray or spread butter and set aside. Preheat oven to 350°F.
On the stove, melt chocolate and butter together. Stir constantly.
Remove from heat once melted and add sugar and salt, stirring constantly. Add eggs one at a time, beating well to incorporate each. Add the flour and stir just until moistened. Fold in nuts and chocolate chips.
Pour the batter into the prepared baking pan and smooth out with a spatula. Bake at 350°F for 40-45 minutes. Set on wire rack to cool completely before removing from pan and cutting.