Mashed root vegetables with roasted garlic

I created this recipe for the Pickle Barrel chain of restaurants in Toronto. We serve these with beef, fish and chicken entrées. It's a nice change from regular mashed potatoes.

8 cloves of garlic
3 cups peeled and cubed Yukon Gold potatoes
1 1/2 cups peeled and cubed sweet potatoes
1 1/2 cups peeled and cubed parsnips
2 tsp vegetable oil
2 cups finely chopped Vidalia onion
1 1/2 tsp brown sugar
2 tsp finely chopped garlic
2 Tbsp olive oil
pinch of salt and pepper
3 Tbsp chopped parsley

Preheat the oven to 450°F. Wrap the garlic cloves in foil and bake for about 15 minutes or until tender. Allow to cool, remove the skin and set aside.
Place the potatoes, sweet potatoes and parsnips in 3 separate large pots with enough cold water to cover them. Boil the potatoes for about 10 to 15 minutes or until tender, the sweet potatoes for about 10 minutes or until tender and the parsnips for about 20 minutes or until tender. Drain and place in 1 large pot, cover and set aside.
Meanwhile, lightly coat a large skillet with cooking spray, add the oil and set over medium-low heat. Add the onion and sauté for i0 minutes or until softened and browned. Reduce the heat to low, add the brown sugar and garlic and continue cooking for 5 minutes.
Partially mash the potatoes, sweet potatoes and parsnips using a potato masher. Add the roasted garlic cloves, sautéed onion, olive oil, salt and pepper. Garnish with parsley and serve immediately.