For the peanut butter filling: In the bowl of a stand mixer fitted with the paddle attachment, add the peanut butter, confectioners' sugar, butter and vanilla. Mix on medium-low speed until creamy. Shape into 1-inch balls and set on a parchment-lined baking sheet. Refrigerate for 2 hours.
For the chocolate coating: In a heat-proof glass bowl set over a pot of simmering water, add the coconut oil and chocolate chips; melt together, stirring, until smooth and silky. Dip the peanut butter balls in the chocolate and place back on the parchment-lined baking sheet. Let cool until completely set, then refrigerate until ready to serve, up to 24 hours.