At least 24 hours before, freeze the bowl of your ice cream maker.
In a blender, combine bananas, tahini, honey, vanilla, and sea salt. Blend until smooth.
In a medium saucepan over medium heat, whisk egg yolks into milk and cream. Continue whisking, occasionally scraping sides and bottom of pan, until mixture thickens slightly, or reaches 170º Remove from heat and pour into blender with banana mixture. Blend on low until integrated. Transfer to a container and chill completely in fridge.
Roughly chop the bittersweet chocolate and melt it in the bowl of a double boiler (or a glass bowl nestled into the top of a pot of boiling water). Transfer melted chocolate to a pouring measuring cup.
Process chilled custard in an ice cream maker according to manufacturer’s instructions. In last two minutes of churning, add vodka. Pour in the melted chocolate in a thin stream. Chocolate will immediately harden into small bits and streaks. If churning is disrupted by pouring or clumping chocolate, simply transfer some of the churned ice cream into a freezer-proof container and set in freezer while you finish adding chocolate. Transfer to a freezer safe container, cover with plastic wrap or lid, and freeze at least four hours.