Steam or boil cauliflower until just tender but still firm about 5 minutes. Drain and place in a 2 quart casserole dish
In a medium sized skillet add the bacon pieces. Cook until crisp and sprinkle on top of the cauliflower.
In a medium sized saucepan add the butter and melt. Add the flour and cook about a minute until it thickens. Slowly whisk in the milk and add in cheese, salt and pepper. Whisk until cheese is melted and sauce has thickened. Pour evenly over the cauliflower and bacon.
Top with parmesan cheese. Mix bread crumbs with melted butter and sprinkle over the top. Bake at 375 degrees for 20-25 minutes or until bubbly and slightly brown at the top.