Preheat the grill until medium hot.
Place the red chilli and red peppers on a baking tray, drizzle with olive oil and place under grill for 5-8 minutes until the skins start to blacken. Remove the tops from the peppers and chillies, cut and seed, removing skin, then finely chop. Set aside.
Melt the Stork Margarine in a large frying saucepan. Add the red onions and cook on low heat for 6-7 minutes until soft but not browned. Add balsamic vinegar and cook for a further minute. Set aside.
Bring water to boil in small saucepan. Add the Knorr Vegetable Stock Pot and stir well until dissolved.
Remove from the heat and add the Maille Dijon Mustard, Worcestershire sauce and three quarters of the cheese, stirring well until the cheese has completely melted. Set aside to cool.
Meanwhile, toast the slices of bread on either side until golden. Place them on a baking sheet and spoon the onions and chopped peppers over each slice, so they are completely covered. Add the cheese sauce mixture, sprinkle with the remaining cheese.
Place the rarebits under the hot grill until dark golden and bubbling.