Preheat the oven to 430 °F. Reduce the heat accordingly if using a fan oven.
Take your garlic bulb – or select 6 large cloves if you want it less garlicky – and remove some of the loose skins. But do not unpeel it all the way. Rub with olive oil and wrap it in foil.
Cut the red peppers in half. Remove and discard the cores, veins and seeds. Then place the peppers skin-side up on a baking tray lined with parchment paper. Add the foil-covered garlic.
Leave any small chillies whole for roasting. Cut large chillies in half if you want to scrape out the seeds and membranes for a milder harissa paste – or roast them whole too. Add the chillies to the tray containing the red peppers and garlic.
Place the tray in the hot oven for 25 to 30 minutes until the red pepper skin is wrinkly and charred in places. Remove any small chillies, if using, after 15 minutes of roasting and rotate the tray before returning it to the oven.
If you are using dried chillies, add them to a heatproof bowl and completely cover them with boiling water. Leave for 20 minutes to rehydrate. Once rehydrated, drain the soaking water, pull out the stems and remove the seeds of the large chillies. Wear gloves if you are using your hands to remove the seeds! Roughly chop the flesh and set aside until needed.
Once roasted, pile the peppers on a plate and cover with an upside-down heatproof mixing bowl, or use cling film. You want them to steam a little while they cool down so that the skins are easier to peel off. Leave aside until cool enough to handle.
Place a large pan on medium-high heat and, once hot, toast the spices until fragrant and popping – about 3 minutes. Shake the pan from time to time for even toasting. Tip the toasted spices into a spice grinder and blitz until ground – or use a mortar and pestle.
Once the roasted peppers are cool enough to handle, remove their skins. Most of the skin should come off without effort. You can leave the small stubborn pieces. Open the foil parcel – be mindful of steam when hot – and pop out the garlic cloves. They won’t be completely soft, but they will already be sweeter. Pick 6 to 8 large garlic cloves and store the rest in the fridge for quick weeknight flavour boosters. Or – if you are feeling particularly garlicky – use all the cloves.
Roughly chop the garlic, peeled peppers and chillies. Add them to a food processor with the rehydrated chillies, spices and a tablespoon of lemon juice. Blitz everything together into a coarse paste, scraping down the sides if needed.
Place 5 tablespoons of olive oil in the large pan you used for toasting spices. Add the red pepper mixture from the food processor and place the pan on medium heat. Add the rose petals and half of the rose water. Stir until the paste and oil are combined and bring to a simmer. Reduce the heat to medium-low and simmer, uncovered. Cook for 30 to 40 minutes, stirring occasionally. The paste is ready once the mixture is darker and there is no more liquid from the peppers, only the wonderfully flavoured red oil seeping from the paste. Add 1 teaspoon of salt and the remaining rose water. Taste and season with more salt if necessary. Don’t be alarmed, the spiciness will subside a touch once it cools down!
Transfer the paste to a sterilised glass jar and cover it with olive oil. The olive oil helps to preserve the paste. Store the sealed container in the fridge for a month. You can also freeze the paste in an ice cube tray for quick pops of flavour.