In the same skillet, heat 1 tablespoon of butter over medium-high heat. Add the chopped onions and stir-fry until lightly golden brown, about 2-3 minutes. Add another tablespoon of butter, then the mushrooms and continue frying, stirring frequently, for another 2-3 minutes, until the mushrooms a lightly browned.
Add another tablespoon of butter, let it melt, then stir in the rice. Continue stir-frying for another 3-4 minutes, until the rice starts to turn golden brown and smell a little nutty. Add the garlic, and continue cooking for about 20-30 seconds.
Carefully and slowly pour in the hot broth while stirring. Watch out for steam and liquid splattering as you begin to pour broth into a hot skillet.
Return the beef and any remaining marinade back into the skillet. Stir well and make sure that the liquid in the pan is boiling. Lower the heat to low, cover the pan with a lid and cook for 10 minutes, undisturbed.
Remove from heat and check If there is still some liquid left at the bottom of the pan. If so, cook covered for another few minutes until most the liquid is gone. Remove from heat an stir well.
Garnish the beef fried rice with chopped scallions, parsley and cherry tomatoes before serving.