Step #1 Mix flour, baking powder, & caster sugar in a medium bowl.
Step #2 Mix egg & milk together; add to dry ingredients & stir just until all the lumps disappear.
Step #3 Cook finely-sliced apples, sugar, & cinnamon in 1-2 tbsps melted butter over med-heat/flame in a non-stick skillet until soft.
Step #4 Put into a small bowl, set aside to cool.
Step #5 Clean & dry the skillet & place over medium-high heat (you may need to adjust down a little if you have a newer-style range; mine is quite old).
Step #6 Melt butter and, when just starting to foam, drop in spoonfuls of batter & flatten them a little with the spoon.
Step #7 Cook without moving the skillet until holes appear in the surface.
Step #8 Carefully flip & cook another min to two mins on the other side until golden brown & carefully crisped (or soft, depending on how you prefer your flapjacks).
Step #9 Serve with a scoop of vanilla ice cream, the spiced apple sauce, & a drizzle of maple syrup.