Skis chattering when skiing steep slopes

I have this issue on my left ski too sometimes (my left leg is the weaker one).

Specific things to try: 1) check that left ankle is flexed and that foot is pulled back under you (not in front of you) as you start the turn, 2) check that you have most of your weight on your left leg, 3) make sure you keep your left leg "soft" rather than braced. An extra maneuver that really helps is "hiking" the new inside hip up and forward a bit as you go into the turn (the "barstool" move); this gives an extra "oomph" to the edging process by providing more angulation.