Clean and cut in cubes of 2 cm the red cabbage, beetroot (leave the skin) and red peppers and set aside.
In a pan, add the olive oil and cook the chopped onion until soft and transparent. Add the rosemary and cook another minute. Add the chopped vegetables and make them sweat. Add half the water and the frozen chestnuts and cook on medium heat for 20-25 minutes or until the beetroot is soft.
In the meantime, chop or crush the hazelnuts to smaller pieces and transfer to a baking tray. Toast them in the oven at 160 C degrees for 15 minutes. Set aside.
When the veggies are soft, remove from the stove and add the remaining water – the coldest water possible will help to take the temperature down and make it easier to blend. In 2 batches, transfer to a blending jar and add vinegar, black pepper and salt. Blend each batch for 40 to 60 seconds or until it’s very smooth. Transfer to a clean pan and heat it up again.
Once the hazelnuts are toasted, transfer to a small bowl and add the hazelnut oil. Serve each soup with roughly a teaspoon of the toasted hazelnuts you just made.
I hope you will enjoy this red cabbage and chestnut soup and that it will keep you warm on cold winter nights.