I leave the skin on because I like the earthy flavor, but you can peel it off if you want a smoother texture and cleaner white color.
Preheat your oven to 400F/200C.
Cut the sunchokes into bite-sized chunks and toss with a little salt and pepper, and about 1 Tbsp olive oil.
Roast in the oven for about 30 minutes or until they start to turn brown and a bit crispy.
Meanwhile, heat about 1 Tbsp butter or olive oil in a heavy pot and saute the onions and garlic on medium-low until soft and translucent (about 10 minutes).
Add the roasted sunchokes to the pot and pour in 1 cup of stock - it should just cover the sunchokes.
Bring to a boil then turn to low and cover with lid.
Simmer for 20-30 minutes until the sunchokes are nice and soft.
After 20-30 minutes, add 1 cup of milk to the pot and cook on low for another 5 minutes.
(NOTE: If you don't have a food processor or mixer/blender of some kind, mash the sunchokes with a fork or masher before adding the milk. )
If you have a food processor/mixer, blend the soup into a smooth consistency.
Add a little more milk or stock if it's too thick.
Adjust the taste with salt and pepper.
Serve into bowls and garnish with parsley or chives.