Before starting, preheat the oven to 425°F. Wash and dry all produce. Cut sweet potatoes into 1/4-inch rounds. Halve Brussels sprouts. Add sweet potatoes, Brussels sprouts, onions, thyme sprigs, half the garlic salt and 2 tbsp oil to an unlined baking sheet. (NOTE: For 4 ppl, use 2 baking sheets, with 2 tbsp oil per sheet.) Season with pepper, then toss to combine.

Roast veggies in the middle of the oven, flipping halfway through, until golden-brown and tender, 22-24 min. (NOTE: For 4 ppl, roast in the middle and bottom of the oven, rotating sheets halfway through.)

Meanwhile, combine maple syrup and mustard in a small bowl. Set aside.

Heat a large non-stick pan over medium heat. While the pan heats, pat chicken dry with paper towels. Season with pepper and remaining garlic salt. When the pan is hot, add 1 tbsp oil (dbl for 4 ppl), then chicken. Cover and pan-fry until golden-brown and cooked through, 6-7 min per side.**

Remove the pan from heat, then add maple-mustard sauce. Flip chicken to coat.

Discard thyme sprigs. Divide veggies between plates, then top with chicken. Drizzle any maple-mustard sauce from the pan over chicken and veggies.