In a heavy large sauce pan, whisk together the sugar, cornstarch and salt.
Put on medium-high heat.
Immediately add and whisk the cold milk and yolks.
Continue to keep whisking while the mixture is heating up for 10 to 15 minutes.
Once it starts to thicken and bubble, turn off burner and take the pan off heat.
Add the vanilla, white chocolate chips, and cold butter pieces-- one by one while you are still whisking.
Place paper cups onto a flat tray or baking dish.
Spoon the custard into each paper cup 3/4 full.
Top with candy pieces or berries.
Finish by poking the wooden sticks into the middle of the custard.
Freeze for 6 hours minimum or over night.
Before eating, tear and peel away the paper cup.
Makes 18 frozen pops.