Heat olive oil in a large skillet. Saute white onion, shallots, and garlic for about 5 minutes. Next add in sweet potato, garlic powder and salt and pepper for 10 minutes. (Be careful - the sweet potatoes might stick to the bottom of your pan so make sure there is enough olive oil to coat them!)
While sweet potatoes are cooking, make the sauce. In a small saucepan, mix all ingredients together. Easy as that! Bring to a boil - add in corn starch + water mixture if you prefer a thicker sauce.
Then add in mushrooms, bok choy, bell pepper and peas. Stir together gently. Add in brown rice (or you can substitute with Quinoa).