Cook bacon pieces in a heavy-based frypan until they begin to crisp. Add breadcrumbs and stir to coat, and cook for a further 3-4 mins until golden. Stir in pepper and remove from heat. Allow to cool before stirring through grated parmesan.
Clean the pan, add oil and heat to medium. Cook sage leaves until crispy. Drain on paper towel.
Scatter bacon breadcrumbs over prepared potato bake, garnish with crispy sage leaves.