Cut the tomatoes in half and put them on a shallow baking tray.
Lightly bash the garlic cloves (with skin on) and tuck these between the tomato halves.
Season with salt and pepper, scatter the oregano all over, drizzle with the olive oil.
Bake in medium hot oven for about 30 minutes until the tomatoes have softened.
Discard the garlic skin then transfer the tomatoes & garlic cloves into a pan or into a dish to cool if you want to chill/freeze them for later use.
5 minutes before you’re ready to serve the soup, add 500 ml of stock to the pan, heat it up to simmering point.
Using a hand-held blender, whizz until you get a silky, smooth soup. Add the basil leaves and balsamic vinegar and whizz again. (Add more stock, if the soup is too thick).
Serve with some feta crumbled on the top, or croutons and/or crusty bread.