French Potage with Pistou

Potage:
2 T. vegan butter
2 medium leeks, white and pale green parts chopped (4 cups)
1/4 cup dry white wine
4 cloves garlic, minced
1 large russet potato, peeled and diced (2 cups)
3 medium carrots, chopped (3 cups)
4 sprigs fresh thyme
1 bay leaf
4 cups low-sodium vegetable broth

pistou:
1 cup firmly packed basil leaves
1/4 cup walnuts, toasted
1 clove garlic, peeled
1/4 cup olive oil

potage: melt butter in large saucepan over medium heat. Add leeks and pinch of salt; cover and cook 5 to 7 minutes or until leeks are softened, stirring often. Stir in wine and garlic, and cook, uncovered, 1 to 2 minutes, or until most liquid has evaporated.
Add potato, carrots, thyme, bay leaf, broth, and 2 cups water. Season with salt and pepper; cover and bring to the boil. Reduce heat to medium-low and simmer 30 minutes, or until potato and carrots are soft.
Remove thyme sprigs and bay leaf. Puree soup in blender or food processor until smooth. Season with salt and pepper.

Pistou: place basil, walnuts, and garlic in blender. Pulse to combine. Pour in oil and blend until smooth. Add water if necessary to form smooth paste. Season with salt and pepper. Serve dollop on top of potage.