Preheat oven to 350 degrees and grease a 9x13-inch baking pan.
In a large bowl, use a wooden spoon to stir together the brownie mix, oil, water, and eggs, stirring until mixed really well.
Stir in pecans, semi-sweet chocolate chips and 1 cup of white chocolate chips.
Transfer batter to prepared baking dish. Bake for 26 to 30 minutes, or until set in the middle.
Sprinkle the remaining 1 cup of white chocolate chips on top. Return baking dish to the oven for 1 minute.Use an offset spatula to spread the white chocolate chips out.Note: If you have difficulty spreading them, leave them as they are.
In a medium bowl, whisk together all frosting ingredients until smooth.Pour frosting over brownies. Spread it out into an even layer.
Let the frosting set up for 20 minutes before cutting into squares.