These charred baby leeks with walnut romesco are proof that a really good side dish just needs contrast. Smoky, tender leeks with blackened edges, served on a rich, vibrant romesco made with sweet roasted red peppers, crunchy toasted walnuts and sharp sherry vinegar. It’s just as good at a summer barbecue as it is alongside a Sunday roast.

The idea comes from Catalonia, where charred calçots, a type of long, sweet spring onion, are traditionally grilled over open flames and dipped into romesco. Baby leeks are a brilliant British stand-in. Charring them on a hot griddle pan softens the inside until sweet and melting, while the outside picks up deep, smoky flavour. Cook them until they’re well coloured and completely tender in the middle, then let them cool slightly and peel away any tough or overly blackened outer layers. Give them a good rinse before cooking, as leeks can hold grit between their layers.

Traditional romesco is usually made with almonds or hazelnuts, but walnuts give a richer, slightly earthier flavour that works beautifully with the smoky leeks. Toasting the walnuts first is important, as it deepens their flavour and adds a lovely nuttiness. Rubbing off any loose papery skins after toasting helps reduce bitterness. Drain the roasted peppers well so the sauce isn’t watery, and blitz until smooth but with a little texture remaining. Sherry vinegar gives the most authentic flavour, but good balsamic or red wine vinegar also work. Season the romesco generously and taste it before serving. It should be bold, sweet, nutty and sharp.

If you can’t find baby leeks, the same method works with tenderstem broccoli, green beans or asparagus, so you can adapt it through the seasons. Naturally vegan and gluten free, this is a great side for barbecues, roast chicken, lamb, steak or grilled fish, and it works well as part of a sharing spread. Do let guests know it contains nuts.

To get ahead, make the romesco up to five days in advance and keep it in a sealed container in the fridge. It also makes a delicious dip or sandwich spread. Char the leeks shortly before serving, or earlier in the day, as they’re just as good at room temperature