This more-or-less-sour was born out of a desire to find a way to combine Aperol and sambuca. While I went with cachaça as the base because of its funky / grassy notes it turns out that you can sub in Bols Genever pretty well. The sweetened condensed milk doesn't change the flavor that much but it does make it beautifully opaque.
0.5 oz lemon juice
1 barspoon (~1tsp) sweetened condensed milk
Shake long with ice, double strain over rocks.
Add ~1oz soda water, finish with 3-4 drops Angostura bitters.