Fill a medium pot with about 2 inches of water and bring it to a gentle simmer over low to medium heat. Find a heatproof bowl that fits snugly over the pot without touching the water.

Place all ingredients—dark chocolate, whipping cream, butter, and granulated sugar—into the heatproof bowl. Set the bowl over the simmering water. Stir continuously with a spatula or whisk as the ingredients begin to melt.

Continue stirring until everything is completely melted, fully combined, and silky smooth. This should take about 5-7 minutes. The mixture will look like thick chocolate pudding. Make sure no lumps of chocolate or streaks of butter remain.

Take the bowl off the water bath and let the mixture cool for about 5 minutes at room temperature. You want it warm but not hot before pouring into molds.

Carefully pour the chocolate mixture into your popsicle molds. If using traditional popsicle molds with sticks, insert the sticks according to your mold's instructions (usually after 30-60 minutes of partial freezing, or immediately if your mold has a built-in lid).

Place the molds in the freezer and freeze for at least 6 hours. For best results, freeze overnight. The popsicles need to be completely firm to hold their shape when unmolded.

To remove the popsicles, run the outside of the mold under warm water for 10-15 seconds to gently loosen them. Pull the popsicles out by the stick. Serve immediately.