Put the milk chocolate into a medium bowl. Heat the heavy cream and corn syrup in a small saucepan over medium heat just until it boils. Pour the cream over the chocolate and let sit for 1 minute.
Using a small spatula, begin stirring the mixture in one direction, concentrating on the center, until it is smooth and glistening. Add the butter and stir until it is completely melted, about 1 minute. Pour the glaze
into a 2-cup measuring cup or a small pitcher. Let cool to 90° to 95°F before using, monitoring the temperature with a candy or instant-read thermometer.
Leftover glaze can be stored, covered, in the refrigerator for up to 2 weeks