1 Preheat the oven to 200°C (180°C in a fan oven), 400°F, gas 6 and line a baking tray with grease-proof paper.
2 Put the sauerkraut in a pan with the stock and bay leaf. Cover and braise gently for around 20 minutes, stirring from time to time. Add extra stock if needed. At the end of cooking, season to taste with salt, ground black pepper and a pinch of sugar.
3 Heat the oil in a frying pan and fry the sausages all over for around 6 minutes.
4 Slice the buns and place a slice of cheese on the bottom half of each bun. Place on the baking tray and cook in the oven briefly until the cheese starts to melt, then remove from the oven.
5 Cut the sausages in half and fill the rolls with sausage, tomato, sauerkraut, rocket and shoots. Secure with wooden skewers and serve with mustard or ketchup if desired.