Unwrap camembert and make incisions in to the rind on both sides.
Slice garlic clove in to small slithers and strip the rosemary sprig of it's leaves.
Push the garlic slithers and rosemary in to the holes in the cheese on both sides. You can use the blunt end of a fork or a chop-stick to push them right inside.
Run the empty camembert box under cold water until it is saturated. Then place the foil covered cheese inside the half of the box and place it onto a baking tray.
Wrap the camembert tightly in foil, leaving the top loosely open.
Pour white wine over the top of the cheese and then loosely close the foil over the cheese and place into the preheated oven.
Heat butter in a saucepan then add the red onions. Keep the onions on a medium heat stirring constantly; add more butter if required. Cook until onions wilt down and go sticky.
When the onions go sticky add balsamic vinegar, salt and pepper to taste.
The onions will be ready when the balsamic vinegar has reduced. Keep it on a low heat stirring occasionally.
Check the cheese; it is ready when it is starting to go really gooey and there is no hardness inside the cheese when you put a knife in.
Take the bread and place it briefly under a cold tap then place in oven directly on a shelf. The water means that the loaf will warm up without burning or crisping up. The loaf is ready when it is warm all over and not damp.
Serve the camembert in its foil, so it stays gooey for longer, with chunks of the warm bread and the balsamic onions.