Can I substitute 70% chocolate for unsweetened chocolate in a cake recipe? This is a recipe for a dark chocolate cake. It calls for 2 ounces unsweetened chocolate. But I made a mistake and bought the 70%. The recipe also calls for 1.25 cups sugar. I don't want it to be too sweet, so by how much should I decrease the sugar? 

The last time I baked this cake, I used 3 ounces unsweetened chocolate and it was perfectly dark. I want to get the same results. Help!
This is a challenge because not only will the different chocolate change the sweetness of the cake slightly but it will change the texture slightly. One thing you can do is subtract the amount of sugar from the recipe that is in the chocolate. In your case 30% of the three ounces of chocolate is roughly one ounce. This should work for you.