1. To make the pancakes, sift the flour into a large bowl with a pinch of salt. Make a well in the centre and add the eggs and a little of the milk. Whisk together until well mixed.  Whisking continuously, add the remaining milk, the sugar and Calvados.
2. Heat a 25cm non-stick frying pan and lightly oil the base. Add enough batter into the hot pan to cover the base.  Heat for 45-55 seconds on each side, until golden. Keep the pancakes warm.
3. Pour the apple filling into a pan, add the toffee.  Heat gently until just simmering but not boiling.
4. Pour the custard into a small pan and heat gently for 2-3 minutes until just simmering.
5. Spoon the custard onto half the pancake and top with the apple filling. Fold the pancake over and serve.