Jessica's Black and White Brownies

Preheat the oven 350 degrees F. Using 2 tablespoons of the butter, grease an 8-inch square-baking sheet. In a metal bowl set over a pot of simmering water, melt the remaining 1/2 cup butter with the white chocolate. In a large bowl whisk together the eggs and sugar. Add the flour, vanilla, baking powder, and salt and mix well. Fold in the pecans and the melted white chocolate. Spread the brownie mixture in the buttered pan and sprinkle the chopped semisweet chocolate over the top. Bake until firm, for about 40 to 45 minutes. Remove from the oven and allow to cool on a rack before cutting into squares. Sprinkle with powdered sugar and arrange in a square sealable plastic container.