Cauliflower and cheddar soup

Ingredients

• 50 ml olive oil
• 30 gm butter, coarsely chopped
• 2 leeks, thinly sliced
• 2 garlic cloves, finely chopped
• 1 cauliflower (about 1kg), coarsely chopped
• 1 large sebago potato, coarsely chopped
• 500 ml (2 cups) chicken or vegetable stock
• 250 ml (1 cup) milk
• 3 each fresh bay leaves and thyme sprigs
• 200 gm crème fraîche
• Finely grated rind of 1 lemon
• 100 gm finely grated vintage cheddar
• Thyme butter
• 2 tbsp olive oil
• 40 gm butter, coarsely chopped
• 1 golden shallot, thinly sliced
• 2 tbsp thyme sprigs
• 1 tbsp lemon juice