1 1/2 cups
, plus more for garnish
fried leeks or crumbled, cooked
, for garnish
Cut off and discard root ends and dark green tops of 3 thin leeks. Cut leeks in half lengthwise. Fan out under cold running water to remove grit. Thinly slice. Melt 2 tbsp butter in a large pot and set over medium heat. Add leeks. Saute, stirring often, until softened slightly, about 5 minutes.
Meanwhile, peel and coarsely chop 6 medium sweet potatoes and 2 carrots. When leeks have softened, add potatoes, carrots and a generous sprinkle or fresh thyme or pinches of dried thyme leaves. Stir in two 900 mL cartons or chicken or vegetable broth. Cover and bring to a boil over high heat, then reduce heat to medium. Cover and gently boil, stirring occasionally, until very tender, about 30 minutes.
Ladle half into a food processor and puree until smooth. Stir in 1 1/2 cups grated old cheddar until melted. Ladle soup into bowls and garnish with more grated cheddar, if you wish. Garnish with fried leeks or crumbled cooked bacon and snipped fresh chives.