Put the flour and 1 /2 tsp salt in a bowl. Combine the eggs with the milk and oil, then gradually pour into the dry ingredients, whisking constantly until it’s a smooth batter. Transfer to a large jug.
Swirl a little oil around a large, non-stick pan over a gentle heat. Pour a quarter of the batter into the pan, tilting to coat the entire base. Cook for 1 min, flip over and cook for a further 30 secs. On one half of the pancake, add 1 /4 of the butter and sprinkle over 1 /4 of the ham and cheese. Grind over some black pepper and fold the pancake over the fillings. Fold in half again and transfer to a plate to serve. Repeat until you have four pancakes. Serve scattered with the chives.