Mix butter, sugar, mashed potatoes, vanilla extract, and peanut butter thoroughly.
Use a teaspoon to shape into eggs. Place on a waxed paper lined cookie sheet.
Chill at least two hours (or overnight).
Melt chocolate in a double boiler. (If you don't have a double boiler, you can use a heatproof mixing bowl on top of a pot of simmering water. Just make sure there is space between the bottom of the mixing bowl and the hot water.)
Dip the cooled eggs one at a time into the melted chocolate. (Use a fork to lower them, cover them, and then scoop them out. Tap them to let excess chocolate drip off. Then use a knife to slide them from the fork back on to the waxed paper lined cookie sheet.)
Allow to chill for one hour.