Preheat oven to 425 degrees. Line a baking sheet with foil or parchment paper.

Lay bacon slices on baking sheet in even layer, transfer to oven, and bake until bacon turns a slightly darker color, but is still very flexible, around 5-7 minutes, depending on thickness of bacon (be careful to not overcook, or you won't be able to wrap the bacon around the asparagus bundles). Remove bacon from oven and set aside to cool. Keep baking sheet out as you'll use it again.

To a small pot over medium low heat, add maple-flavored syrup, butter, salt, and pepper and bring to a light boil, whisking occasionally. Remove from heat and set aside.

Split asparagus stalks into 8 groups. Wrap cooled bacon slices around grouped asparagus stalks, starting about 1/2 inch from the bottom, and secure bacon slice with toothpick. Transfer bacon-wrapped asparagus bundles to casserole dish.

Pour syrup mixture into casserole dish atop bundled asparagus and sprinkle half of grated parmesan (~10g) on top. Bake for 35-40 minutes.

While asparagus bundles cook in oven, place baking rack atop foil- or parchment paper-lined line baking sheet you used previously.

Remove casserole dish from oven and transfer baked asparagus bundles to baking rack (rotating them so the side that was baked down is now up), turn on oven broiler, and broil until bacon is crispy, about 1-2 minutes.

Remove baking sheet from oven, remove toothpicks from bundles, sprinkle remaining grated parmesan on top, and allow to cool slightly prior to serving.