Pre-heat the oven up to 375 degrees.
Line the bottom and sides of an 8 x 8 inch baking pan with foil.
Grease the foil with shortening.
In a medium bowl, sift together flour, cocoa powder, and salt.
Set aside.
Melt butter in a large saucepan over low heat, stirring frequently
until smooth. Off the heat, mix in the sugar until smooth. Then
beat in the eggs, one at a time, until each is incorporated. Beat
in the flour mixture and when mixed, fold in the milk chocolate
and white chocolate baking chunks.
Pour into the prepared pan and bake until a toothpick inserted
in the center comes out almost clean (about 50 minutes).
Carefully transfer the brownies, still in the foil, onto a rack
to cool completely.
To serve, cut into 16 squares and peel away the foil.