First, you need to preheat your oven up to 400°.
Prepare a large mixing bowl. Then, toss your Brussels sprouts onto this bowl. Season the sprouts with olive oil, onion and garlic powder, salt, and pepper. Make it evenly smeared for all sides of the sprouts.
Prepare a tray, and put a non-sticking baking sheet. Proceed with placing your Brussel sprouts on it.
Once the preheating is done, put your Brussel sprouts into the oven. Roast it for 10 minutes. This time, the objective is to soften the Brussel sprouts that it makes cutting the sprouts easier to do.
Ten minutes passed, remove the vegetable from oven and start cutting it into halves. Toss it back onto the baking sheet.
Now, sprinkle a generous amount of freshly grated Parmesan cheese.
Once you put back the vegetable to the oven, roast it for additional 15 minutes before stirring it. This stirring is done to avoid one side getting too much burned.
Continue for another 15 minutes. Then, check back to stir once again.
For the last roasting time, you only need to allocate 10 minutes. Check the vegetables and avoid having it too brown.
Once you see the grated cheese starts to brown and forming crispy edges, you can stop the roasting. Take your tray of delicious vegetables out.
Serve on a large serving plate. The yield is for 6 portions.