When I'm feeling fancy, I tend to reach for champagne. That champagne is then usually promptly deposited into a mason jar for sipping.
Sometimes I like my fancy dressed down a touch, i.e., champagne in a mason jar, Keds with a date-night dress. You know, that sort of thing.
It's sort of like this. This silky, flowery custard with satiny gin berry glaze is super duper fancy. You totally deserve fancy. And since everything tastes better in a mason jar (and since 4 oz. mason jars are some of the cutest containers around), this custard deserves to be housed in one. This is fancy-dressed-down dessert. Which works out well with all the post-custard-consumption jar-licking I see in my future. So fancy.