In 2-quart cellophane bag, layer ingredients in the following order: granulated sugar, cocoa powder, baking soda, flour, brown sugar, chocolate pieces, and pecans. Seal; store in cool, dry place for up to 1 month.
To make brownies:
Preheat oven to 350 degrees F. Lightly grease 13x9x2-inch baking pan; set aside. In large bowl, combine two eggs and 1 cup melted butter. Add brownie mix from bag; stir until combined. Spread batter in prepared pan. Bake for 30 minutes. Cool in pan on wire rack. Cut into bars. Makes about 32 brownies.