Roasted Cauliflower and Leek Soup
1 head cauliflower, broken into florets 1 quart chicken stock 1 tablespoon cracked black pepper 1 teaspoon dried chervil 1 teaspoon kosher salt 2 cloves garlic, minced 2 leeks, white part only, chopped 2 tablespoons vegetable oil 3 tablespoons butter ¼ cup all-purpose flour ⅓ cup heavy whipping cream