See below

In hors-doeuvre trays, cut them in half take out the yolks & mash
them with a little dijon mustard & mayonnaise until its a light
consistancy but not runny. Take the egg white part & fill the cavity
with the caviar of your choice. Fill the cavity of a small pastry
tube withh a star tip & top the caviar with the yolk mixture. Now if
your on a limited budget or can take or leave the caviar, do the
opposite. Fill the white with the yolk mixture & top with caviar.