1 (16-ounce) box shell pasta
2 cups cauliflower florets, streamed slightly & roughly copped
1 cup broccoli florets, cut into bite-size pieces
1 cup fresh spinach leaves, roughly chopped
16 ounces shredded extra sharp white cheddar cheese, divided
4 tablespoons butter
3 1/2 cups milk
4 tablespoons all-purpose flour
2 teaspoons black pepper
1 teaspoon salt
1 cup panko bread crumbs