Preheat oven to 425 degrees F.

In a small bowl, toss quince slices with 1 tablespoon each olive oil and maple syrup. Arrange slices on a rimmed baking sheet and slide into the oven. Roast for 15 - 20 minutes, turning halfway through. Pull quince once the edges are lightly browned and the fruit is tender, but not limp. Set aside to cool.

Meanwhile, prep Brussels sprouts. Set out two small mixing bowls (including the one used to toss quince). Using a sharp paring knife, trim stem and very carefully carve out the core. Break off any leaves and set them in one the bowls; set sprout upright and cut into very thin slices, about 1/8-inch thick. Place sliced sprouts in the second bowl. Toss sliced sprouts with your hands and fish out any single leaves and add those to the leaf bowl. Toss sliced sprouts with 1/2 tablespoon (1 1/2 teaspoons) olive oil, 1 teaspoon maple syrup, and a pinch of sea salt. Toss leaves with remaining olive oil and a pinch of sea salt. Roast slices for 15 minutes, flip, scatter reserved leaves, and roast for another 5 - 7 minutes, until leaves are crisp and slices are tender.

To make dressing, combine lemon juice, maple syrup, shallot, mustard powder, and sea salt in a small bowl. Whisk in the olive oil until emulsified. 

Toss quince with warm sprouts and plate. Finish with a few crumbles of goat cheese and a pinch of sea salt. Serve salads warm, drizzling with dressing just before the first bites since dressing will eventually wilt the crispy leaves.