The Professor-Building Chronicles (HP)

The fiancee he'd been longing for turned out to be a fiance, and was having a pretty rough time of it. The protective Yinglong decisively snatched the poor thing away to raise him himself. But how had his adorable little sweetheart turned into a sharp-tongued giant bat? No, wait, a phoenix. A sharp-tongued black phoenix, one he couldn't hit or bear to scold. So all he could do was send him home and keep him hidden away.

Theme: An Harry Potter fanfic that gives the professor a happy ending