Can tempered chocolate be seeded with a different chocolate? I have unsweetened chocolate, which is stored in seized form (soft, grainy). I use it for chocolate sauces. Is it possible to temper this chocolate by:


Sweetening it with white or brown sugar? 
Then seeding it with Some
Callebaut 811 dark chocolate chips that I have? Therefore, the
melted and seeding chocolates are different.


I just recently learned to bake donuts. I tried to glaze it using my regular chocolate sauce recipe made a little thicker. Wasn't good. I revisited tempering chocolate, and thought that having it crystallize over the donut would be perfect and less messy.
You cannot use sugar unless you do not mind having crunchy sugar crystals. There is no way of sweetening chocolate by adding sugar, even powdered sugar, without a conche. I think if the cacao contents are not too dissimilar, you should be fine. I have got away with 70% seeding 85%, but I cannot tell you whether you could get away with any mix. You can also sweeten your 100% by mixing sweet dark chocolate.

I would not use whole chips though, you want it grated. In fact, I would temper the Callebaut first and grate it. Keep a stash of that as seed. I have also routinely tempered dark chocolate without seeding.