Using stand mixer fitted with whisk, whip egg yolks on medium-high speed until thickened and pale, about 1 minute. Gradually add sugar and whip until completely dissolved, scraping down bowl as needed, about 2 minutes; reserve.

Heat milk and half-and-half just to simmer in medium saucepan over medium heat. Using stand mixer fitted with whisk, whip reserved yolk-sugar mixture on medium-low speed, gradually adding hot milk mixture until combined, about 2 minutes. Transfer mixture to now-empty pot and cook over medium heat, whisking constantly, until mixture registers 160 degrees, about 30 seconds.