Efforts to "fix" the fudge aren't likely to succeed. The fudge making process is a one way trip: you cook sugar syrup to a certain temperature, and then add butter and volatile flavorings like vanilla as it cools. At a certain point you beat the fudge, which causes the sugar to form zillions of very small crystals instead of fewer larger ones, and this is where the fudge gets that smooth fudgy texture. To fix your fudge, you'd need to heat it again so that you could dilute the cocoa with something -- more sugar perhaps. But even if you heated it back to the point where the crystals would melt again, you won't get the same crystallization process happening because you've already added the butter.
Your best bet is to start over. Give the first batch to someone who likes intense chocolate, or just throw it out. The cost of the ingredients is small and your time is valuable -- don't bother trying to fix the result of an irreversible process.