Substituting Chocolate for Cocoa
I thought this was going to be an easy question. Normally you could substitute 3T cocoa and 1T oil for each 1 oz square baking chocolate so you'd probably be able to get away with the opposite. But you also have to take into account the sugar that they add to the 70% and reduce that in you recipe. I also can't find any specifics for the percent chocolate in baking chocolate so I don't know how it compares to your 70%. I'm voting for trial and error...how bad can it be to have a few "imperfect" chocolate recipes sitting around the house waiting to be eaten?