Directions:

Preheat the oven to 450 degrees F. Butter a 2-quart gratin dish and coat the sides with Parmesan cheese.

Place Brussels sprouts on a rimmed baking sheet, toss with olive oil, and roast until just tender, about 15 minutes. Let cool slightly and coarsely chop, leaving plenty of large chunks.

Meanwhile, melt the 1 1/2 tablespoons butter in a medium saucepan, then whisk in flour; cook for 1 minute. Stir in the half-and-half and cook until thickened slightly, about 1 minute. Add the seasoning mix and Brussels sprouts and transfer mixture to the prepared gratin dish.

Sprinkle with breadcrumbs and the 1/4 cup Parmesan cheese and bake until browned and crisp on top, about 25 minutes. Let rest for at least 10 to 15 minutes before serving.