Combine semisweet chocolate chips and sweetened condensed milk in a medium saucepan over low heat. Stir gently until fully melted and glossy, about 5 minutes.
12 oz semisweet chocolate chips, 14 oz sweetened condensed milk
Remove pan from heat and stir in orange zest, orange juice, and vanilla extract until fully combined and fragrant.
Pour mixture into a shallow bowl, cover, and chill in the refrigerator until firm, about 2 hours.
Scoop 1-inch portions with a small spoon or cookie scoop, then roll each between your palms to form balls.
Dust each truffle in unsweetened cocoa powder, then chill another 15 minutes before serving.
0.5 cup unsweetened cocoa powder
Notes
During my first trial, I overheated the ganache and it became grainy—stirring gently over low heat solved this.I discovered that wide, sweeping motions in the pan keep the texture silky and eliminate air bubbles.Chilling the truffles on parchment paper before rolling prevents sticking and speeds up shaping.