- 5 tablespoons butter
- 1 pound oyster mushrooms, cut into 1-inch-wide pieces
- 15 ounces frozen whole petite onions (about 2 1/2 cups; do not thaw)
- 1 pound small brussels sprouts (about 4 cups), trimmed, halved
- 2 1/2 cups low-salt chicken broth
- 2 garlic cloves, minced
- 1 1/2 tablespoons chopped fresh thyme
- 1 1/2 tablespoons all purpose flour
- 2/3 cup whipping cream
- 1 cup fresh breadcrumbs made from crustless French bread
- 1/2 cup freshly grated Parmesan cheese
- Butter 8x8x2-inch glass baking dish. Melt 1 tablespoon butter in large nonstick skillet over medium-high heat. Add mushrooms; sauté until juices have cooked away, about 10 minutes. Transfer mushrooms to large bowl.
- Melt 1 tablespoon butter in same skillet over medium-high heat. Add onions; sauté until brown and tender but still holding shape, about 6 minutes. Add to bowl with mushrooms. Melt 1 tablespoon butter in same skillet over medium heat. Add brussels sprouts; sauté until browned, about 10 minutes. Add 1/2 cup broth to skillet. Cover and simmer until brussels sprouts are tender, stirring often, about 10 minutes. Uncover and cook until liquid evaporates, about 1 minute. Add to bowl with mushrooms.
- Melt 1 tablespoon butter in same skillet over medium heat. Add garlic and thyme; sauté 1 minute. Add flour and stir 1 minute. Gradually add remaining 2 cups broth and cream and bring to boil, whisking often. Boil until reduced to 1 1/4 cups, about 8 minutes. Mix sauce into vegetables in bowl. Season with salt and pepper. Transfer vegetables to prepared dish. (Can be made 3 days ahead. Cover and chill.)
- Preheat oven to 375°F. Melt 1 tablespoon butter in small saucepan. Mix in breadcrumbs and cheese. Sprinkle crumb mixture over vegetables. Bake uncovered until vegetables are heated through and topping is golden, about 35 minutes.