In a medium saucepan bring 2.5cm water to the boil. Add broccoli; return water to the boil. Reduce heat, simmer covered until crisp-tender (approx 3 minutes); set aside.
In a large non-stick frypan, cook bacon over medium-high heat until nearly crisp (about 4 minutes). Add onion, stirring frequently, until the onion is crisp tender and the bacon is crisp (approx 4 minutes).
Stir in vinegar and cook until vinegar is reduced by half, about 30 seconds. Add mushrooms, salt and broccoli; toss to coat.