Preheat the oven to 220°c.
Add the sprouts, onion, balsamic vinegar, garlic, 1/2 stock pot and sweetener to the roasting dish and mix until coated.
Spray the tops of the sprouts with low calorie cooking spray and place in the middle of a hot oven.
After 20 minutes, toss the sprouts and spray with more low calorie cooking spray.
Place back into the oven for 10 - 20 minutes, until the liquid has reduced and the sprouts are tender. They should be glossy and dark with a few crispy bits.
Season with salt and pepper to taste and serve hot.