Broccoli Gratin with Mustard-Cheese Streusel

Preparation Melt butter in large nonstick skillet over medium-high heat. Add onion and garlic; sauté until onion is soft, about 4 minutes. Mix in dry mustard, then 2 tablespoons Dijon mustard, blending well. Add breadcrumbs; sauté until crumbs are crisp and golden, stirring and pressing with back of fork to separate, about 8 minutes. Season with salt and pepper; cool completely. Mix in 3/4 cup cheese. Cook broccoli florets in large pot of boiling generously salted water until crisp-tender, about 3 minutes. Drain. Transfer to paper towels; cool. (Streusel and broccoli can be made 1 day ahead. Cover separately and refrigerate.) Preheat oven to 350°F. Butter 13x9x2-inch glass baking dish. Place broccoli in large bowl. Add whipping cream, remaining 2 tablespoons Dijon mustard, and 1/4 cup cheese; toss to coat evenly. Arrange broccoli in prepared dish. Sprinkle streusel over. Bake until broccoli is heated through and streusel is browned, about 30 minutes.

Preparation Melt butter in large nonstick skillet over medium-high heat. Add onion and garlic; sauté until onion is soft, about 4 minutes. Mix in dry mustard, then 2 tablespoons Dijon mustard, blending well. Add breadcrumbs; sauté until crumbs are crisp and golden, stirring and pressing with back of fork to separate, about 8 minutes. Season with salt and pepper; cool completely. Mix in 3/4 cup cheese. Cook broccoli florets in large pot of boiling generously salted water until crisp-tender, about 3 minutes. Drain. Transfer to paper towels; cool. (Streusel and broccoli can be made 1 day ahead. Cover separately and refrigerate.) Preheat oven to 350°F. Butter 13x9x2-inch glass baking dish. Place broccoli in large bowl. Add whipping cream, remaining 2 tablespoons Dijon mustard, and 1/4 cup cheese; toss to coat evenly. Arrange broccoli in prepared dish. Sprinkle streusel over. Bake until broccoli is heated through and streusel is browned, about 30 minutes.