Mix the egg yolk and mustard in a bowl, and spread the mixture evenly over the ham. Sprinkle with the bread crumbs and crushed gingersnaps.
Bake the ham in the oven at 475 Fahrenheit (250 Celsius), or make it golden brown with a kitchen blowtorch. (The breadcrumbs should become golden brown.) If you use the oven, 5 to 10 minutes should be enough.
Serve the ham at room temperature with sautéed cabbage and mustard.