Brussels Sprouts and Grapes au Gratin

Directions

1. Preheat oven to 400°. In a large saucepan, bring 1/2 in. water to a boil. Add Brussels sprouts; cook, covered, until crisp-tender, about 5 minutes. Drain and transfer to a greased 8-in. square baking dish. Add grapes.
2. Meanwhile, in a small saucepan, melt butter over medium heat. Stir in arrowroot flour until smooth; gradually whisk in milk. Bring to a boil, stirring constantly; cook and stir until thickened, 5 minutes. Add salt and pepper. Pour over Brussels sprouts and grapes.
3. Top with shredded Swiss cheese. Sprinkle with grated Parmesan. Bake until bubbly, about 20 minutes.