Heat the olive oil and butter in a large saucepan until the butter has melted. Sweat the onion and cabbage for 10-12 minutes, stirring occasionally, until softened. Add the vegetable stock and simmer for 10 minutes.
Remove from the heat and purée using a stick blender until smooth. Add the Crème fraîche and seasoning and whisk well. Preheat the grill to hot.
Keep the soup warm over a low heat. Grill the bacon for 4-5 minutes, turning once until golden and crispy. Ladle the soup into serving bowls and garnish with a couple of rashers of bacon.
Freezing and defrosting guidelines
Make the soup, then leave to cool at room temperature. Freeze (without garnishes or toppings) in a rigid container, leaving a bit of space for expansion, for up to 1-3 months. Reheat either from frozen or defrost in the fridge overnight. Once piping hot, add toppings or garnishes and serve.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.