Step 1

Preheat oven to 450°F. Melt butter in a medium saucepan over medium-high heat. Add garlic; cook until fragrant, 30 seconds. Add flour; cook 30 seconds, then whisk in broth. Bring to a boil and cook 1 minute.

Step 2

Add Broccolini, cover, and cook 2 minutes. Uncover and add gnocchi; cook 2 minutes. Remove from heat. Stir in chicken, Gruyère, and 1/4 cup Parmigiano. Season with salt and pepper.

Step 3

Divide mixture among four 12-ounce baking dishes (or transfer to one large baking dish or ovenproof skillet). Sprinkle with remaining 1/4 cup Parmigiano. Bake until bubbly in center and golden brown on top, about 15 minutes (20 minutes if baked in one dish). Let stand at least 15 minutes before serving.