Preheat oven to 450 degrees F. Microwave 1 tablespoon butter in a microwaveable bowl on High until melted, about 30 seconds. Stir in panko; set aside.Advertisement
Set a large bowl filled with ice water near the stove. Bring a large pot of water to a boil. Add asparagus; cook until bright green, about 1 minute. Drain; plunge the asparagus into the ice water. Let stand for 5 minutes; drain. Arrange the asparagus in a 9-by-13-inch baking dish.
Return the pot to the stove; heat over medium-high heat. Add the remaining 2 tablespoons butter, stirring to coat. Add garlic; cook, stirring constantly, until fragrant, about 1 minute (do not brown the garlic). Add flour; cook, stirring often, for 30 seconds. Gradually whisk in milk; bring to a boil, whisking constantly. Continue cooking, whisking constantly, until the mixture thickens, about 5 minutes. Remove from heat; stir in cream cheese, mozzarella and salt.
Pour the cheese mixture over the asparagus in the baking dish, stirring to coat. Sprinkle evenly with the panko mixture. Bake until the asparagus is tender, 12 to 15 minutes.
2 fat, 1 vegetable, 1/2 whole-milk dairy