Potato Leek Soup with Lemon

Heat the oil in a large pot over medium heat. Sauté the onions for about two minutes, or until softened and slightly browned.
2 teaspoons olive oil, 1 small onion
Add the potatoes, leeks, and garlic, and cook for another 3-4 minutes, stirring frequently to prevent sticking*. Add the thyme, salt, and pepper, followed by the vegetable broth.
400 grams (14 oz) potatoes, 2 medium leeks, 2 cloves garlic, 1 tablespoon thyme, 1 teaspoon salt, ½ teaspoon pepper, ¼ teaspoon cayenne pepper, 1 litre (4 cups) vegetable broth
Increase the heat to high and bring the soup to a rolling boil, covered. Add the beans.
250 grams (1 ½ cup) cooked or canned white beans
Reduce the heat and simmer for 20-25 minutes, or until the potatoes can be easily pierced with a fork.
Remove from the heat and add the lemon juice and zest. Taste and season as needed, then puree with an immersion blender to the degree you'd like (or don't blend at all).
Zest and juice of a lemon
Serve immediately. Leftovers keep well in a sealed container in the refrigerator for a couple of days and can be frozen.