Fennel soup with star anise, hazelnuts and tarragon

• 50 g unsalted butter
• 1 onion, thinly sliced
• 2 heads of

Heat the butter in a pan, add the onion and fennel and cook for about 12-15 minutes, until softened. Add the potatoes, milk, 600 ml water and hazelnuts and bring to the boil. Add the star anise and simmer for 25 minutes or until all the vegetables are very soft. Remove the star anise and transfer t