Preheat the oven to 400°F. As noted, the most time efficient way to roast. the squash is during the second bake for the baked brie stuffing, so I would recommend planning that accordingly.
Toss the squash with a bit of olive oil, salt, and pepper.
Spread the butternut squash cubes in a single layer on a baking sheet and roast in the preheated oven for 25-30 minutes, or until tender and slightly caramelized. Remove from the oven and allow them to cool to room temperature. Store in the fridge on a plate, covered with foil until the following day.
FOR THE DRESSING:
In a bowl, whisk together the Dijon mustard, tahini, sherry vinegar, and water until well combined. Add more water if necessary to thin it out. Add freshly ground black pepper to taste. You can also add a pinch of salt if desired, but remember that the Parmesan cheese will also contribute saltiness to the salad.
FOR THE SALAD:
PREP NOTE: Chop all your ingredients when your squash is in the oven, then store in the fridge until ready to assemble the following day.
Assemble the shredded brussels sprouts, most of the Parmesan,pomegranate arils and roasted squash in a bowl. Toss with the pomegranate arils and roasted squash in a bowl. Toss with the dressing right before serving. Top with more pomegranate arils, parmesan slices and black pepper for garnish.