Slow cooker beef bourguignon

Name: Slow cooker beef bourguignon
Ingredients: 3 tbsp vegetable oil; 1 ½kg stewing or braising steak, cut into small chunks; 2 large onions, chopped; 2 carrots, chopped; 2 celery stalks, chopped; 2 bay leaves; 2 thyme sprigs or rosemary sprigs; 3 tbsp plain flour; 750ml bottle red wine; 1 beef stock cube; 1 tsp caster sugar; 2 tbsp tomato purée; 100g unsmoked bacon lardons; 6 small shallots or baby onions, halved or quartered; 300g closed cup mushrooms, halved or quartered; mashed potatoes or crusty bread, to serve