On olive oil and butter, soften the diced onion, add the peeled carrot sliced thinly, and sauté, stirring occasionally, for 2 minutes.
Add the peeled and diced potatoes and sauté again for about 5 - 7 minutes, stirring from time to time. Season with salt and pepper.
Add the fresh cauliflower cut into small florets and sauté together for a moment (add frozen cauliflower later). Pour in the hot broth and bring to a boil. Cover and simmer for about 20 minutes until vegetables are tender. Halfway through that time, add the frozen cauliflower florets, rinsed beforehand in a sieve under hot water.
Remove the soup from heat, add the chopped dill and chives. Mix the sour cream with a few tablespoons of cold water, then with a few tablespoons of broth. After tempering the sour cream, add it gradually to the soup while stirring constantly. Serve with bread.