Cook the potatoes in a pan of slightly salted water, drain and let them cool.
When cooled, cut them into thin slices.
Cut the frankfurters into small pieces.
Grease a deep baking dish and add a layer of potatoes. Scatter some beans/peas, olives, frankfurters and some spinach leaves on top, then spoon half the tomato sauce to cover the veggies well. Season with plenty of ground pepper.
Repeat the layering, finishing off with the tomato sauce or cheese, if used.
Chill until you’re ready to bake.
Preheat the oven for 180°C then bake for about 25 minutes or until the top is golden.
Serve warm.