Heat 2 tbsp oil in a large pot over high heat. Add half the mushrooms, and cook for 5 minutes until golden. Season with salt and pepper then remove and set aside.
If the pot is dry, another 1/2 - 1 tbsp oil, and add butter. When melted, add onions and garlic.
Cook for 30 seconds, then add remaining mushrooms. Cook for 5 minutes or until mushrooms are lightly browned.
Add rice and a splash of broth. Mix so the brown stuff on the bottom of the pot mixes into the liquid.
Once the base of the pot is clean, add remaining liquid. Place lid on, bring to a simmer then turn down to medium low.
Cook for 15 minutes or until there is no residual liquid.
Remove from stove, remove lid, QUICKLY toss in reserved mushrooms and scallions, put lid back on. Leave for 10 minutes.
Fluff rice using a fork or wooden spoon.
OPTIONAL: Stir in more butter.
Notes
BROWN RICE: Follow recipe but use 2 1/2 cups liquid for tender, fluffy rice (or 2 3/4 cups for soft rice) and it will take around 45 minutes to cook on the stove (check at 35 minutes, then every 5 minutes until liquid is absorbed).