1. Melt butter in a small skillet over medium-high heat. Add breadcrumbs and cook, stirring, until toasted, 2 to 3 minutes. Set aside.
2. Preheat oven to 425°F. Place asparagus on a rimmed baking sheet, and drizzle with olive oil; toss to coat. Sprinkle with salt and pepper. Bake until tender, 12-15 minutes.
3. While asparagus cooks, place heavy cream in a small skillet. Bring to a gentle simmer over medium heat, stirring occasionally. Add Dijon mustard and Parmigiano-Reggiano 1/4 cup at a time, stirring until completely melted and smooth after each addition.
4. Arrange asparagus on a platter. Spoon cheese sauce over asparagus, and sprinkle with breadcrumbs and lemon zest.