My soft chocolate cookies are soft but still too crumbly. How should I fix it?
One think I would try is changing up the egg white to egg yolk recipe by multiplying the other ingredients by 1.5x and adding an extra yolk. Egg yolks are a source of emulsified fat and they keep cookies fudgier (and chewier). For other variables you can tweak, you might look at J. Kenji Lopez Alt's guide to chocolate chip cookies. He takes each ingredient 1 by 1 and changes it up to see how it effects his cookie texture. Your cookies are going to be a little different thanks to the extra fats from the chocolate (hence why I think an emulsifier would help), but it should still be a helpful resource.