Mix the flour, a large pinch of salt, the eggs and milk to a smooth batter. Leave to rest for 30 minutes, then stir in the melted butter and herbs.
Heat some vegetable oil in a non-stick pan. Pour in a small ladle of dough and tilt the pan to evenly coat the base of the pan.
Fry the crepe for 1-2 minutes until golden underneath, then turn and cook the other side until golden. Repeat to use up all the batter, stacking the cooked crepes on a plate.
Wash the rocket, shake dry and spread over the crêpes.
Cover the rocket with the ham.
Scatter the drained olives on top.
Roll up the crêpes and serve.