Creamy Leek Soup with Potatoes

Ingredients:

• 400 g potatoes (about 3 small tubers), peeled and cut into small cubes
• 450 g leeks, washed and cut off the dark green part, about 4-5 medium stalks
• 3 tablespoons unsalted butter
• A generous pinch of coarse salt + more to taste
• 1 liter of vegetable broth
• 1 cup heavy cream
• 1 cup of sour milk or kefir
• 0.5 tsp white pepper
• 1 tbsp chopped chives

Preparation:

1. Finely chop the leek.
   
   In a 6-quart saucepan, melt the butter over medium heat. Add the leeks and a generous pinch of salt and sauté for 5 minutes. Reduce the heat to medium-low and sauté, stirring occasionally, until the leeks are tender, about 25 minutes.
2. Add the potatoes and vegetable broth, increase the heat to medium, and bring to a boil. Then reduce the heat to low, cover, and simmer until the potatoes are tender, about 45 minutes.
3. Turn off the heat and puree the soup with an immersion blender until smooth. Add heavy cream, sour milk, and white pepper. Taste and adjust the seasoning with salt if needed. Sprinkle with chives and serve immediately, or refrigerate the soup and serve cold.