With a spoon, dig one 1 1/2" and two 3/4" holes in the flour mixture. Put the oil in the big hole and vinegar and vanilla in the small holes.
Pour the milk over everything and mix to the consistency of mud.
Bake for 15 minutes, then sprinkle on the marshmallows. Continue baking for 10 to 15 minutes, or until the center springs back when pressed lightly and the marshmallows have melted into tan "moon rocks" (hence the name of the recipe). Set the pan on a rack to cool and serve right out of the pan.