In a medium saucepan, bring heavy cream and espresso powder to a simmer. Remove from heat, add chopped unsweetened chocolate, and let sit for 5 minutes to melt.
Whisk in powdered Swerve Sweetener and butter until smooth. Refrigerate for 1 hour until firm.
Roll 1 tablespoon of mixture into balls and place on a waxed paper-lined cookie sheet. Freeze for 1 hour.
Melt dark chocolate chips and cocoa butter in a heatproof bowl over simmering water, stirring until smooth.
Dip frozen truffles into melted chocolate, coating evenly. Tap off excess and place back on the baking sheet.
Melt white chocolate chips in a separate heatproof bowl over simmering water, stirring constantly.
Drizzle melted dark chocolate over half the truffles and white chocolate over the rest. (Use a snipped ziploc bag for piping).
While chocolate drizzle is warm, place one espresso bean on top of each truffle. Let set.