In a bowl, combine all of the ingredients mixing very thoroughly
Divide evenly between the oatcakes and, with the back of a spoon press gently to smooth it over the surface of each oatcake.
4 hardboiled eggs, chopped finely
6 oz./175g boiled or roast ham, trimmed of fat and very finely diced
4 rounded tablespoons mayonnaise
1 teaspoon Dijon mustard
About 10 grinds of black pepper