Step 1

Preheat oven to 180°C/160°C fan-forced. Line a baking tray with baking paper. Place garlic on prepared tray. Drizzle with half the oil. Roast garlic for 12 to 15 minutes or until tender. Stand for 10 minutes or until cool enough to handle. Squeeze garlic from skins. Discard skins.

Step 2

Meanwhile, heat remaining oil in a saucepan over medium-high heat. Add leeks, celery and 1 tablespoon thyme. Cook, stirring, for 5 to 7 minutes or until tender. Add stock, 2 cups cold water and potatoes. Cover and bring to the boil. Reduce heat to medium. Simmer, uncovered, for 12 to 15 minutes or until potatoes are tender. Add garlic.

Step 3

Remove from heat. Transfer to a processor. Process soup until smooth. Stir in 1/2 cup cold water and remaining thyme leaves. Return to medium heat. Cook for 2 minutes or until heated through. Season with salt and pepper. Serve.