Continue to beat while adding cooled milk mixture, a little at a time, until fully incorporated, stopping to scrape down sides as necessary. (tofufortwo.net)
Add the cooled milk mixture from the saucepan and whisk to thoroughly combine. (thewickednoodle.com)
Add in the cooled milk mixture and beat on high speed until it's a whipped cream consistency, several minutes. (goldenbarrel.com)