My recipe combines cream cheese, egg yolk, and baking powder. Spread bread rounds with mayo, then layer of devilled ham and dollop of cream cheese mixture. Sprinkle with paprika and bake as directed or freeze.
This sounds easier but with same flavors (I don't use onion juice or horseradish but they would be good) and I'll try it. I don't toast the bread, though. If you use the very thin Pepperidge Farm you don't need to as it will crisp.