In a saucepan, whisk together milk and tapioca flour, then whisk in cocoa. Whisking constantly, bring to a boil; reduce heat and simmer, stirring often, for 5 minutes. Remove from heat and whisk in chocolate, until melted, thoroughly incorporated and smooth. Stir in condensed milk and vanilla. Set aside to cool.

Pour into molds and freeze until slushy, then insert sticks and freeze until solid, for at least 4 hours. If you are using an ice pop kit, follow the manufacturer’s instructions.