Put the tomatoes, sugar, stock and sauces into a medium pan with some salt and pepper. Bring to a simmer and cook for 5-10 mins. Stir in the mascarpone and blend to a smooth soup. Return to the pan and keep warm while you make the dippers.
Heat the grill to high and toast the ciabatta until golden. Rub with the garlic, season, then top with the cheese and grill until melted and golden. Slice into fingers and serve with the soup, sprinkled with the basil, if using.