Preheat your oven to 190° C (375° F), get out a 7x11 inch baking pan.
Measure the evaporated milk and add water until the measuring cup reads ¾ cup. Pour into a mixing bowl.
To the mixing bowl, add the ham, rice, cheese, soup, and onion. Mix together.
Spoon ½ of mixture into the baking pan and spread out evenly.
Top with the asparagus spears.
Add remaining soup mixture onto of the asparagus in an even layer.
In a small bowl, mix together the crushed corn flakes and butter. Sprinkle on top of casserole.
Bake for 25-30 minutes or until heated through and the top is lightly browned.
Serve with sides of your choice, enjoy.