1/2 cup half-and-half
2 shots coffee-flavored liqueur, such as Kahlua
2 shots vodka
1 shot of vanilla syrup
2 scoops coffee ice cream
Combine half-and half, Kahlua, vodka and vanilla syrup, and blend with a spoon until completely smooth.
Divide between two chilled glasses and fill them about 3/4 of the way full. Top each off with seltzer water and stir to combine. To serve, hang a cold scoop of ice cream off the side of each glass.