In a medium bowl, add the milk, heavy cream, white sugar, milk powder, and cornstarch. Whisk vigorously until everything is completely dissolved and there are no lumps whatsoever. The mixture should look smooth and uniform.

Pour the mixture into a non-stick pan. Turn the heat to low. Cook the mixture while stirring continuously with a spatula or whisk. Do not walk away! Low heat and constant stirring prevent the bottom from burning and the mixture from forming lumps. Keep stirring until the mixture thickens and becomes silky smooth, like a thin pudding. This usually takes about 3-5 minutes. Once it's thick and coats the back of your spatula, turn off the heat immediately.

Remove the pan from the heat. Add your crushed Oreo pieces (cream removed) to the warm mixture. Stir until they are evenly distributed throughout. Set the mixture aside and let it cool completely to room temperature. This step is important — don't skip it!

Allow the mixture to come to room temperature naturally. Do not pour warm or hot liquid into your popsicle molds — it can warp plastic molds, create condensation that turns into ice crystals, and cause uneven freezing. Patience here pays off.

Once cooled, pour the mixture evenly into your popsicle molds. Cover with the lid (if your molds have one), and place them in the freezer. Freeze for at least 4 hours, but overnight is even better. The popsicles need to be completely solid from center to edge.

When you're ready to enjoy your popsicles, remove the molds from the freezer. Run the outside of the molds under warm water for 10-15 seconds — just enough to loosen them. Gently pull the popsicles out. Serve immediately. If you're using the same silicone molds as me, just unmold directly — no need to run them under water.