Heat the oven to 170°C/ 150°C fan/gas 3½. Add the tomatoes, garlic cloves and chilli flakes to several baking trays, drizzle generously with olive oil and season with plenty of salt. Roast for 45-60 minutes, swapping the trays halfway through, until the tomatoes are caramelised.
Add another drizzle of olive oil to a large saucepan over a medium heat. Add the shallots and gently cook for 10 minutes until very soft, then add the roasted tomatoes. Take the garlic cloves and squeeze the flesh out of the skins using the side of your knife, then add this too (discard the skins). Add the oregano and chicken stock, bring to the boil, then simmer for 10 minutes. Remove from the heat, use a stick blender to whizz until smooth, then cool and chill until ready to serve (see Make Ahead).
Heat the oven to 190°C/ 170°C fan/gas 5. Put the grapes on a baking sheet, drizzle with olive oil and season with salt. Roast for 20 minutes, then cool. 4 Serve the chilled soup scattered with the roasted grapes, chopped courgette and tomatoes, and a generous drizzle of extra-virgin olive oil.
