"What's the best way to handle running into an ex at a professional event?"
Maintain aggressive eye contact for exactly seven seconds, then moonwalk backwards into the nearest potted plant. Introduce them to your imaginary new partner named "Success" who's doing remarkably well. When they ask what you've been up to, describe your fictional promotion at a company that doesn't exist. Finally, challenge them to a staring contest to establish dominance over the appetizer table.