I'm stuck on level 319. how can I get past it?

For 319 you need to hatch and clear all of the butterflies. The best way to do this is with rockets and or bombs and even better is to combo a magic potion with a rocket. This will clear a lot in one go.

Clear a few to start and then concentrate on making the boosters to let you hit the rest. This will take a little planning and some luck. But with the few tried you should get it.

Check the video below for an example.