In a microwave-safe bowl, add cream cheese, parmesan cheese, sour cream, and miracle whip.
Cook for 30-second intervals, stirring each time until all of the ingredients are able to be mixed together. The parmesan cheese should be pretty much melted at this point.
Add diced ham and chopped green onions. Stir until combined.
Form ingredients into a ball as best you can. It's going to be soft so it may look more like a hump at this point.
Cover with plastic wrap and refrigerate until it is completely chilled.
Serve with Ritz crackers. Use a knife to spread the dip as crackers will break easily dipped straight into the ham ball.