Well, you could try that and see what happens! If all you want is color and a hint of taste, replacing a tablespoon or so of flour with cocoa might do it... but I really don't know what a "box mix" entails here. (The classic "pound cake" is pretty darn simple ingredientwise: flour, butter, eggs, sugar in equal weights. Why a mix?) Really adding *chocolate* to any kind of cake requires substantially rebalancing the recipe.
2/24/13 at 9:52pm