2 cups 1919 Root Beer
2/3 cup whole milk
1/2 cup sweetened condensed milk (from 1 [14-oz.] can)
3 tablespoons evaporated milk (from 1 [5-oz.] can)
1 teaspoon vanilla extract
Pour 1919 Root Beer into a large glass measuring cup, and let stand, uncovered, in refrigerator 8 hours or up to overnight. (This is to let it go flat and to keep it chilled.)
Whisk together whole milk, condensed milk, evaporated milk, and vanilla in a glass measuring cup; chill until ready to use.
Carefully pour 1 1/2 ounces of flat root beer (about 3 tablespoons) into each of 10 (3-ounce) ice pop molds. Freeze molds 1 1/2 hours. Remove from freezer, and insert ice pop sticks into partially frozen root beer. Return to freezer, and freeze 1 hour.
Remove ice pop molds from freezer, and top root beer layer with milk mixture, filling almost to top of mold, leaving 1/4- to 1/8-inch at the top. (You may not use all the mixture; discard any remaining.) Return ice pops to freezer, and freeze until completely frozen, about 4 hours.
Gently run bottom of molds under hot water to remove ice pops.