For the Romesco sauce, firstly pre-heat the oven to 220C. Rub a little oil all over the peppers and bake in the oven for 10 minutes until blistered, remove from the oven, allow to cool slightly, then peel and roughly chop.
Then thinly slice the chilli and garlic. Heat the oil over a medium-high heat and roast the almonds until evenly toasted, add the chilli, garlic and breadcrumbs, cook for a minute or so, then transfer to a blender.
Add the sherry vinegar, passata, basil and peppers and blend until smooth. Check the seasoning and serve.