Preheat oven to 350°. In a 5- to 6-quart pan over high heat, bring about 3 quarts water to a boil. Rinse broccoli and trim off and discard tough stem ends; if skin on stalks is tough, peel stalks. Cut broccoli into 1-inch pieces. Add to boiling water and cook just until barely tender when pierced, 3 to 5 minutes. Drain.
Rinse and dry pan. Add 1/4 cup butter to pan and melt over medium heat. Stir in flour and salt until smoothly blended; cook until bubbly, about 1 minute. Add milk and stir over medium-high heat until mixture is boiling and thickened, about 3 minutes. Add cream cheese and gorgonzola; whisk until smoothly blended. Stir in broccoli. Pour into a shallow 2 1/2- to 3-quart casserole.
In a blender or food processor, whirl bread cubes into coarse crumbs; you should have about 1 1/3 cups. In a small bowl, mix crumbs with 1 tablespoon melted butter. Sprinkle evenly over broccoli mixture.
Bake until casserole is hot in the center and crumbs are golden, 20 to 30 minutes.