In the bowl of a stand mixer fitted with the paddle attachment, beat confectioners’ sugar and meringue powder at low speed until combined. With mixer on low speed, add ¾ cup (180 grams) warm water in a slow, steady stream, beating until mixture fluid, about 1 minute. Increase mixer speed to medium, and beat until stiff, 4 to 5 minutes. Store in an airtight container for up to 3 days.