In a large bowl whisk together olive oil, canola oil, vinegar, sugar, ½ tsp salt & pepper each and soy sauce.
Add broccoli, mushrooms and onion and toss together.
Sprinkle with basil, dill and garlic and again toss everything together until thoroughly saturated and seasoned.
Cover and refrigerate for at least 8 hours. Occasionally stop to toss vegetables during this time period so the oil/vinegar mixture gets distributed over all the vegetables while it works to tenderize them.
Recipe by How to Have it All at https://www.howtohaveitall.net/broccoli-mushroom-salad-recipe/