Chop the dark chocolate and tofu into small pieces.
Melt the dark chocolate using a microwave or a double boiler.
Blend the dark chocolate, tofu, unsweetened cocoa powder, and stevia smoothly in a blender.
Line a square mold with parchment paper and pour in the mixture, leveling it out.
Let it set in the refrigerator for at least 2 hours.
Cut into bite-sized pieces and sprinkle cocoa powder on top.