Forgot the yeast in a brioche bread recipe
I will sometimes add yeast late, for instance when I'm not finding a sourdough culture to be adequate for a decent rise, or on the rare occasion when I'm getting poor performance from a particular batch of yeast. 

I typically dissolve it in a small amount of water (or milk for this recipe), work the mixture into the dough, and add a bit of flour if needed to compensate for the added liquid. 

It works.