Turn oven to 350° Put the butter in an oblong casserole dish, and stick in the warming oven to melt. When it's melted, sprinkle half the brown sugar over the hot butter.
Cut the bread into ¾-inch slices. Spread half the slices with cream cheese and the other half with strawberry preserves. Make sandwiches from the slices. You will likely have about 10 sandwiches.
Beat together the eggs, milk, and vanilla. Dip each sandwich into the egg mixture, and arrange the sandwiches overlapping in two rows in the casserole dish. When all the sandwiches are in the dish, pour the rest of the egg mixture over the bread. Sprinkle the top with the remaining brown sugar.
If baking right away, let the French toast sit at room temperature for 5 or 10 minutes to sbsorb all of the egg mixture. Otherwise, cover tightly with foil and refrigerate until ready to bake--up to 48 hours later. Bake at 350° for 30 to 45 minutes until the custard is cooked and the tops of the Frech toast is getting a little crisp.