Step 1: 1. Heat the butter, onions, garlic on a medium heat.
Step 2: 2. Once the onions have softened stir in the mushrooms.
Step 3: 3. Add the stock and the potatoes once the mushrooms have gained some colour.
Step 4: 4. Season with salt and pepper and cook until the potatoes are soft (about 10 minutes).
Step 5: 5. Stir in the milk and horseradish and cook for a further 5 minutes.
Step 6: 6. Liquidize and enjoy!