1. Preheat oven to 375°F. Scrub the sunchokes under cold water with a stiff brush. Slice into 1/4 inch slices. Peel and cut onion into quarters. Grab an oven proof dish and add the sunchokes and onion. Toss with olive oil and sprinkle with salt and fresh cracked pepper. Place in oven and cook for about 1 hour or until fork tender.
2. In a medium sized sauce pan make a roux with the flour and canola oil. Cook the flour in the oil on low heat until a very light golden color. Add the stock, sage, roasted sunchokes, roasted onions, pepper, and salt.
3. Take an immersion blender and puree until smooth. Cook for an additional 10-15 minutes until thickened. Add stock if needed. Makes about 6 servings.