This is the quintessential summer fun treat. Fudge popsicles are unbeatable when homemade. These are creamy, supremely chocolatey, and the perfect way to cool off.
Place chocolate chips in a small glass bowl and microwave on 50% power for 30 seconds. Stir and repeat until chocolate is smoothly melted.
In a medium saucepan, combine the melted chocolate, sugar, cornstarch, cocoa powder, and milk. Stir over medium heat until mixture thickens, 10 mimutes. Remove from heat. Add vanilla extract and butter, stirring to incorporate.
Let mixture cool just until it is warm (not hot) and stir again. Pour into 6 large popsicle molds (or 8 smaller molds.)