Celeriac Soup

Bahan-bahan (5 porsi)

• 60 g / 4 tbsp butter (, unsalted)
• 2 g arlic cloves (, finely chopped)
• 1 onion (, diced (brown or yellow))
• 1/2 leek (white part only) (, diced into 1cm / ½" cubes (~ 3/4 cup, Note 1))
• 3 celery stems (, diced into 1cm / ½" cubes (~1 1/2 cups))
• 800 g / 1.6 lb (peeled weight) celeriac (, cut into 2cm / ⅘" cubes (~1kg / 2lb unpeeled, Note 2))
• 200 g / 7oz potato (, peeled, cut into 2cm / 4/5" cubes (floury or all-rounder – about 1 large; Note 3))
• 1.5 litres / quarts (6 cups) water (, or stock if you prefer)
• 1 1/2 tsp salt
• 1/4 tsp white pepper
• 1 cup cream (, full fat (pure, thickened or heavy, Note 4))
• 1 bay leaf (, fresh)
• 2 thyme sprigs
• 1/2 tsp black peppercorn ((go without if no sachet))
• 1/2 tsp coriander seeds ((1/8 tsp powder if no sachet))
• Croutons ((Note 6))
• Olive oil (, for drizzling)
• 1 tbsp chives (, finely chopped (sub parsley or chervil))