In a medium bowl, combine 400g milk, 40g white sugar, 70g whole milk powder, and 15g glutinous rice flour. Whisk vigorously until the mixture is completely smooth with no lumps whatsoever. Pay special attention to the milk powder — it tends to clump, so take your time here.

Pour the mixture into a non-stick pan. Turn the heat to low — and I mean low. This is not a step to rush. Stir constantly with a spatula or wooden spoon, scraping the bottom and sides of the pan as you go. After a few minutes, you'll notice the mixture starting to thicken. Keep stirring until it becomes thick and silky, similar to a thin pudding or a milkshake. This usually takes about 3-5 minutes. Do not let it boil vigorously — a gentle simmer at most.

Turn off the heat. Pour the thickened mixture through a fine-mesh strainer into a clean bowl or a large measuring cup with a spout. This catches any tiny lumps that might have formed. Let the mixture cool to room temperature — do not skip this step. Pouring hot liquid into plastic or silicone molds can cause warping, cracking, or leaking. If you're in a hurry, place the bowl in an ice bath or pop it in the fridge for 10-15 minutes.

Once cooled, pour the mixture evenly into your popsicle molds. Tap the molds gently on the counter to release any air bubbles. Insert the sticks, cover with the lids (if your molds have them), and place carefully in the freezer. Freeze for at least 4 hours — overnight is even better. The popsicles need this time to set completely so they unmold cleanly.

To unmold, run the outside of the molds under warm water for 10-15 seconds — just enough to loosen the edges. Gently pull the sticks. If they don't come out easily, run warm water for another 5 seconds and try again. Never yank or force them. If you're using silicone molds, you can simply push them out directly. Serve immediately and enjoy that creamy, nostalgic, ice-crystal-free bite.