Before starting, preheat the broiler to high. Wash and dry all produce. Peel, then cut onion into 1/4-inch slices. Heat a large non-stick pan over medium heat. When hot, add 1 tbsp oil (dbl for 4 ppl), then onions. Season with salt. Cover and cook, stirring occasionally, until slightly softened, 3-4 min. Uncover, then add half the fig spread and 2 tbsp water (dbl for 4 ppl). Cook, stirring occasionally, until onions are dark golden-brown, 5-8 min. Remove the pan from heat, then transfer onions to a plate.

Meanwhile, halve buns. Core, then cut apple into 1/4-inch matchsticks. Whisk together vinegar, remaining fig spread and 1 tbsp oil (dbl for 4 ppl) in a large bowl. Add apples, then toss to coat. Cut brie in half, through the centre, parallel to the cutting board.

Arrange buns on an unlined baking sheet, cut-side up. Spread mustard on bottom buns, then top with brie halves, cut-side up. Spread onion mixture on top buns. Broil in the middle of the oven until brie is warmed through, 2-4 min. (TIP: Keep an eye on buns so they don't burn!)

Add arugula and spinach mix and carrots to the bowl with apples and dressing. Season with salt and pepper, then toss to combine.

Stack some salad on top of brie, then close with top buns. Cut sandwiches in half. Divide sandwiches and remaining salad between plates.