A question about a recipe: Sweet Potatoes Anna with Prunes

I have a question about step 5 on the recipe "Sweet Potatoes Anna with Prunes" from mrsp. It says:

"Put a layer of potatoes, overlapping in circles, in the dish. Brush with clarified butter, and salt and pepper. Put another layer of potatoes and about half the prune pieces. Salt and pepper. Brush with clarified butter. Repeat two more layers, embedding the rest of the prunes at the end and brushing each layer with clarified butter and salt and pepper. You can do four layers of potatoes or six, it's up to you. Pack the potatoes tightly. If there's a little butter left at the end, it's no big deal." Peel the potatoes, or not? Step 5