Combine butter, finely chopped onions, poppy seeds, and Dijon mustard in a bowl.

Mix until well blended.

Refrigerate the mixture for 24 hours to allow flavors to meld.

Remove the butter mixture from the refrigerator and allow it to return to room temperature for easier spreading.

Bake biscuits according to package directions.

Once the biscuits are baked and slightly cooled, spread each biscuit with the prepared butter mixture.

Add a slice of shaved ham to each biscuit.

Cover the prepared biscuits with foil to prevent them from drying out.

Warm the covered biscuits in a preheated oven at 350°F (175°C) for 10 to 15 minutes, or until heated through.