Preheat the oven to gas mark 6, 200°C, fan 180°C, and bring a large pan of salted water to the boil.
Toss the tomatoes and chili with 1 tbsp oil, season well, and transfer to a roasting tin.
Roast for 15 mins until the tomato skins have burst open.
At the same time, put the almonds and hazelnuts on a tray and roast for 5-7 mins until the shade is darker and aromatic.
Set aside both to cool.
Put the nuts into a food processor and pulse on and off until coarsely ground.
Remove to a bowl. Add the tomatoes, chili, paprika, garlic, and vinegar to the processor and blitz until smooth.
Stir in the nuts and season to taste.
Cut off most of the more brutal green ends of the leeks and trim the root ends, taking care not to take off too much to prevent them from falling apart during cooking.
Cut the leeks in half lengthways and rinse under running water to remove any grit.
Add to the boiling water and cook for 3-4 mins, until almost tender.
Drain and pat dry.
Set a griddle pan over medium heat.
Drizzle the remaining 1 tbsp oil over the leeks.
Place on the griddle pan and fry for about 6 mins, turning now and again, until charred on all sides and completely tender.
Arrange the leeks onto a platter and dollop over some of the romesco sauce, serving the remainder in a bowl alongside.
Scatter over the parsley and serve immediately. This can be refrigerated for up to 2 days and reheated in the oven
