To make the soup, heat the oil in a large saucepan and gently fry the onion and garlic for 5 minutes until beginning to soften. Stir in the tomatoes then refill the can with water and pour into the pan. Add the herbs, 2 tsp of the sugar, a good pinch of salt and plenty of freshly ground black pepper. Bring to a gentle simmer and cook for 15 minutes, stirring occasionally.
Remove from the heat and blitz the soup with a stick blender until as smooth as possible – or cool for a few minutes then blend in a food processor and return to the saucepan. Stir in the cream and adjust the seasoning to taste, adding a little more sugar if necessary. Set aside while the sandwiches are cooked.
To make the fried cheese sandwiches, spread the bread lightly with butter and top two slices evenly with the cheese, leaving a 1cm boarder around the edge. Sandwich with the remaining bread.
Pour the oil into a large non-stick frying pan and place over a medium-low heat. Add the sandwiches carefully to the pan and cook for about 3 minutes on each side until golden brown and crisp. Warm the soup gently, stirring regularly.
Transfer the sandwiches to a board and cut into quarters. Ladle the soup into deep bowls and serve with the sandwiches.