Spray the inside of a 2 litre / 2 quart casserole dish with cooking spray. Set aside.
Empty the sauce mix into a microwave safe jug or bowl. Disregard package directions and instead measure 1 1/2 cups (12 oz / 350 ml) of water. Add a small amount of that water to the sauce mix, whisk to make a smooth paste, then add the rest of the water and whisk till smooth. Cook in microwave for 2 to 3 minutes until thick, then set aside to let it thicken some more as it stands.
Trim the Brussels sprouts and wash them. Cook them until tender. [1]
Start heating over to 175 C / 350 F / Gas mark 4.
Transfer the cooked sprouts in a large bowl or pot. Add the cheese sauce, mix carefully until all sprouts are coated with sauce. (If the sauce got too thick, you can whisk in a bit more water.) Put in casserole dish.
Rip up the two slices of bread to make fresh bread crumbs. Put in a small bowl, season to taste with herbs of your choice such as oregano, savoury, rubbed rosemary, black pepper, etc. Add the 2 tablespoons of fat-free Italian dressing, stir to mix. Sprinkle the bread crumbs on top the Brussels sprouts, spray the top of bread crumbs lightly with 1 to 2 sprays of cooking spray (this helps them brown better for "curb" appeal.)
Bake for about 35 minutes or until piping hot and bread crumbs are golden brown.