Before starting, preheat your broiler to high. Wash and dry all produce. Core, then cut apple into matchsticks. Cut brie in half, through the centre, parallel to the cutting board. Halve buns. Whisk together vinegar, half the fig jam and 1 tbsp oil (dbl for 4 ppl) in a large bowl. Add apples and toss to combine. 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. Cook until slightly softened, 3-4 min. Add remaining fig jam and season with salt. Cook, stirring occasionally, until onions are dark golden-brown, 4-6 min. Remove pan from heat, then transfer onions to a plate. Carefully rinse and wipe pan clean.

Arrange buns on a 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 it so that it does not burn!)

While sandwiches toast, heat the same pan (from step 2) over medium. Add pepitas to the dry pan. Toast, stirring often, until golden-brown, 4-5 min. (TIP: Keep your eye on them so they don't burn!) Transfer to a plate.

Add arugula and spinach mix and pepitas to the large bowl with apples and dressing. Toss to combine. Season with salt and pepper.

Sandwich top and bottom buns together, then cut in half. Divide sandwiches and salad between plates.