Mix together the two meats in a large bowl adding 2 tbsp of the olive oil to loosen it.
Heat the remaining olive oil in large saucepan. Add the onion and celery to the pan and sweat.
Add the meat gradually, stirring all the time to break down any lumps. Increase the heat, add the red wine and simmer until it has reduced by half.
Add in the puree and chicken stock and lower the heat then throw in the sprigs of rosemary. Put a lid on the pan and leave to cook on a low heat for 2 to 2 ½ hours until you have a rich thick sauce. Season with salt and pepper.