Roast garlic confit

Preheat the oven to 180°C

Break apart the garlic bulbs into cloves and place in a bowl. Add a generous splash of oil to the bowl and toss through the garlic, seasoning well with salt and pepper. Transfer the garlic to a roasting pan and roast for about 30 minutes, or until the skins have puffed and taken on a good colour

When the garlic bulbs are soft enough to pierce easily with a skewer, remove them from the oven and leave to cool. Peel or pop the cloves out from their skins and place in the a large jar with a strong seal. Add the thyme and lemon zest, seasoning generously with sea salt

In a separate bowl, whisk the harissa into 250ml olive oil and pour evenly over the garlic cloves to cover, adding more olive oil if necessary. Seal the jar tightly

Line a large saucepan with cloth and place the garlic jar on top - the pan should be large enough to comfortably hold the jar. Fill the pan with enough cold water to come up to just below the lid of the jar, then bring to the boil. Reduce the heat and leave to simmer gently for 1 hour, topping up with boiling water from the kettle as needed

After an hour remove from the heat and leave to cool completely before removing the jar from the pan. The sealed garlic will keep for several weeks, although once opened they are best kept refrigerated and used within two days