Assuming normal milk doesnt have some magical property due to its ratios (a tale i have read on other message boards) then of course it would work. But so would eating an avacado, nuts, olive oil etc.
I would be more tempted to make whey protein and chocolate milk mixtures. Then again, whey protein and chocolate milk with half and half would be even tastier. This thread makes me lament two things:
1. Im not a hardgainer
2. In Australia we cant get delicious food inventions such as half and half.