Prep broccoli rice. If using frozen, thaw about 40 percent so pieces break apart. If making fresh, process broccoli in a food processor until desired consistency, or chop by hand for a more controlled chop.
In a large skillet over medium heat, melt butter. Add onions and cook until translucent, around 5 minutes. Add mushrooms and carrots and cook until fragrant and slightly browned, around 5-7 minutes. It’s important to brown the veggies as they will be the base of flavor in this dish.
Add garlic and broccoli rice. Raise heat to high and cook, while stirring, until broccoli is cooked through. About 8 minutes. If you’re using fresh broccoli and it starts to look dry, add a splash of hot water, butter or olive oil to keep it moist.
Add parmesan, basil, salt and pepper. Season to taste.
*Frozen broccoli rice is often composed of just the stems so the color tends to be lighter and has less of a broccoli flavor. If you opt for fresh broccoli (and use the green heads) your dish will taste more broccoli-y and a brighter green. Both are delish, so your choice! You could also just use the fresh stems and reserve the heads for a stir fry later.
**Do not overcrowd the pan! You don’t want the broccoli to steam. Keeping a single layer of ingredients is always best. If necessary, use two frying pans if one is not big enough.