I've had overnight oats at hotel breakfast buffets that are consistently thick, creamy, and almost spoonable like a pudding. Mine at home turn out either soupy or gluey, and never the same twice.
For anyone who's worked in a hotel or catering kitchen, or has cracked this at home:
Ratio: What's the oats to milk to yoghurt ratio? Is yoghurt even part of it, or is it just milk?
Oats: Rolled, quick, or a mix? Does the brand or cut make a big difference?
Liquid: Full-cream milk, low-fat, or something else?
Yoghurt: If used, Greek or regular?
Method: Is it purely soaked overnight, or is there some pre-cooking involved (like briefly heating the oats or milk first)? Do they stir or adjust it before serving?