Yeah that can be fixed, clean it out real good, put it in the kiln and bring it up to heat slowly over a a couple hours. Hand torch the jagged part and cut clean. Weld a prepped gong joint (cut and air-blocked) onto the cut stem, even out the weld 1/4 at a time, kiln and anneal. But be prepared to lose the whole piece if the internals on other parts of the piece crack during the initial heat or after the repair.
Better yet, after heating, take the existing stem off at the base, weld a new one in plac e and even out the weld. Kiln and anneal very very slowly.