Before starting, preheat the oven to 450˚F. Wash and dry all produce. Heat a large non-stick pan over medium heat.While the pan heats, peel, then cut onion into 1/4-inch slices.When the pan is hot, add 1 tbsp (2 tbsp) oil, then onions. Season with salt. Cook, stirring occasionally, until slightly softened, 3-4 min.Add 3 tbsp (6 tbsp) fig spread and 3 tbsp (6 tbsp) water. Cook, stirring often, until onions are jammy and dark golden-brown, 5-8 min.Remove from heat, then transfer onions to a small bowl.

Meanwhile, halve buns.Core, then cut apple into 1/4-inch matchsticks.Whisk together vinegar, remaining fig spread, 1 tsp (2 tsp) Dijon and 1 tbsp (2 tbsp) oil in a large bowl. Add apples, then toss to coat.Cut brie into 1/4-inch slices.

Arrange buns on a parchment-lined baking sheet, cut-side up. Spread remaining Dijon onto cut-side of each bun half. Top buns with onion mixture, then brie slices. Bake 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 to the bowl with apples and dressing. Season with salt and pepper, then toss to combine.

Sandwich top and bottom buns together, then cut sandwiches in half. (TIP: Add some salad to the sandwiches before closing, if desired!)Divide sandwiches and salad between plates.