Foolproof Fennel Soup - I Quit Sugar

Ingredients

• 80 g butter.
• 2 large bulbs fennel, sliced (reserve the leaves to garnish).
• 2 leeks, sliced.
• 2 teaspoons fennel seeds or a mixture of fennel and anise seeds and ground liquorice root.
• splash apple cider vinegar or white wine.
• 6 cups chicken stock.
• 2 cloves garlic, chopped.
• 2 red potatoes, chopped - or 1 cup leftover cooked rice.
• yoghurt or sour cream or shaved parmesan, to serve.
• 4 slices pancetta, fried until crisp, cooled and crumbled.
• pinch salt.