House training the cat

We have 2 cats, Yoda and Nalla. Both use a litter box. Yoda though covers his shit. Nalla on the other hand doesn’t. Instead she scratches loudly at the edge of the box until some one comes and covers it for her and cleans out the litter box. Too much of a prima donna to get her paws dirty.
So myself and herself sitting watching TV and make comments like “Your cat needs you”, “No, isn’t she your cat?”
Yesterday I lost and went to scoop while holding my nose. When I got there Nalla (which I’ve just discovered auto corrects as balls on my tablet) gives up all pretense of trying to cover her crap and runs off. Which is quite usual. That’s kind of what she keeps us puny humans around for. That and scratching under her chin.
But, before I could grab the scoop, Yoda jumps in and covers it and hops back out. Which earned him cat treats. Which is kind of why he keeps us around. Now if I can just teach him to pour a scotch…