Hi RosieB I didn't find a recipe for a washing day pancake but did find a wash day pudding. I'm wondering whether it is it so am posting this link (not sure if it will work as I don't remember how to do it). Hope this helps. http://blackpetalsks.tripod.com/blackpetalsissue42/id20.html
Here's another Washing Day Pudding Recipe, without the blended frog in the washing machine!!