Cauliflower Soup

I made this from a Canadian Living recipe, but doubled the amount of roasted cauliflower and oil used. I like the mix of the roasted flavour with cheese and mustard.

2 heads cauliflower, cut into florets
2 Tbsp. olive oil
2 Tbsp. butter
2 leeks (cut in half lengthwise to wash out sand and then slice)
3 cloves garlic, minced
4 cups vegetable stock
1/4 tsp. salt
1 1/2 cups shredded old cheddar cheese
1 Tbsp. grainy mustard
3/4 tsp. pepper

Toss cauliflower with oil and then roast at 425 degrees F for about 45 minutes, turning to brown all sides. Sauté leeks and garlic in butter until soft. Blend cauliflower and leeks with stock in food processor or blender until smooth. You will need to do it in 3 or 4 batches. Add to soup pot along with 1 1/2 cups of water, the salt and pepper and bring to a boil. Stir in the cheese and mustard until melted.