In a medium saucepan over medium heat, bring the heavy cream and espresso powder to a simmer. Remove from heat and add the chopped chocolate. Let sit 5 minutes to melt.
Add the sweetener and butter, and whisk until smooth. Refrigerate until firm, about 1 hour.
Using about 1 tablespoon of the mixture at a time, roll into balls and place on a waxed paper lined cookie sheet. Freeze 1 hour.
In a heatproof bowl set over a pan of barely simmering water, combine the dark chocolate chips and cocoa butter. Stir frequently until melted and smooth.
Dip the frozen truffles in one at a time, tossing with two forks to coat. Lift out and tap the fork on the side of the bowl to remove excess chocolate. Place back on the waxed paper lined baking sheet.
Place the white chocolate in another heat proof bowl and set over the pan to melt, stirring constantly.
Drizzle any remaining melted dark chocolate over half of the truffles and drizzle white chocolate over the rest (Place the melted chocolate in a ziploc baggie with the very corner snipped off to pipe it over).
While the chocolate drizzle is still warm, place one espresso bean on the top of each truffle. Let set.