Sponsored: BBQ Little Willies Sausage burgers with caramelised onions | Sainsbury`s Magazine

Ingredients

• 1 tbsp olive oil, plus extra for brushing
• Small knob of butter
• 1 large red onion, cut into thin wedges
• 1 tsp black mustard seeds
• 2 tsp light soft brown sugar
• 1 tbsp rice wine vinegar
• 160g pack The Vegetarian Butcher Little Willies Sausages
• 1 x half ciabatta, halved lengthways and horizontally
• small handful salad leaves
• tomato relish, to serve