In a large bowl, whisk together the sweetened condensed milk, vanilla, and salt. In the bowl of a stand mixer fitted with the whisk attachment, whisk together the heavy cream and espresso powder on medium to medium-high speed until stiff peaks form, 3 to 6 minutes.
Gently fold the whipped cream into the milk mixture in two installments then place the bowl in the freezer to chill for 30 to 40 minutes. (This initial freezer-time helps set the ice cream so when you swirl in the ganache it stays swirly— and we’re all about the swirl, am I right?)
After 25 minutes, scrape half of the ice cream into the chilled pan, then evenly dollop half of the ganache over the top and swirl it with a paring knife. Repeat with the remaining ice cream and ganache. The pan will be quite full.
Tightly cover in plastic wrap and freeze for 3 1/2 to 5 1/2 hours, depending on how soft you like your ice cream (I’m partial to soft here, in case you were wondering). If frozen solid, let rest briefly on the counter until scoopable. Keep the ice cream, wrapped, in the freezer for up to a week.