Chunk missing from a mug? Answered

So, my grandfather accidentally broke my grandmother's favorite mug, and it shattered into too many pieces to be glued back together. I have a large chunk, but I would need to reconstruct the base with something. Is there a material that I could use (dishwasher safe) to re-form the bottom of the cup? I don't normally do this kind of stuff, but I'd like to do something here.