Winter Lentil Soup (Now with Photo!)

The weather has turned cold and crisp, and that means I crave a lot of soup. I'll try to post a few favorite soup recipes this month. This one serves 4-5, but you can easily double it to feed a crowd.

2 leeks, white & light green parts only, rinsed well
1 bunch kale*
1 tbsp olive oil
1 14oz can diced tomatoes
3 cups water
1 sweet potato, peeled & cut into 1/2" dice
1/4 cup brown lentils
1/2 tsp dried thyme
1 tsp salt
1/4 tsp pepper
fresh basil leaves (optional)
Parmesan (optional)

Halve each leek lengthwise, then slice into 1/4" thick half-moons (about 1 1/2 cups). Remove the stems from the kale; slice the leaves into 1/2" wide strips (about 1 1/2 cups). Heat the oil in a large pot over medium heat. Add the leeks and cook for 3 minutes. Add the tomatoes (undrained) and water and bring to a boil. Stir in the kale, sweet potato, lentils, thyme, salt & pepper. Add basil leaves, if using. Simmer until the lentils are tender, about 30 minutes. (If you don't end up with enough broth for all the vegetables, just add more water.) Ladle into bowls and sprinkle with Parmesan (if using).

*I always have lots of extra kale, so I use the rest of the bunch in another soup recipe.