Combine the coffee beans, milk, sugar, salt, and ½ cup of cream in a medium-sized saucepan. Bring to a simmer over medium heat, but do NOT boil. Stir to dissolve the sugar and remove from the heat when the mixture is warm. Cover with a lid and let steep at room temperature for 1 hour.
Pour the remaining 1 cup of cream into a large bowl and place a fine mesh strainer over the bowl. Set the bowl next to the stove. If the coffee mixture has cooled, re-warm it briefly.
In a separate medium-sized bowl, whisk together the egg yolks. Very slowly drizzle about 1 cup of the liquid from the coffee mixture into the eggs, just a tablespoon or so at a time, while whisking constantly.
Pour the warmed egg yolks into the saucepan and warm over medium-heat while stirring constantly, until the mixture thickens and coats a spatula, about 5 minutes.
Pour the custard through the fine mesh strainer into the remaining cream, press down on the coffee beans to extract as much custard as possible. Discard the coffee beans.
Add the vanilla and the coffee powder to the ice cream mixture and stir to combine. Chill COMPLETELY before processing in your ice cream maker according to the manufacturer's instructions.
Notes
The instant coffee in this recipe is key to highlighting the flavors in this ice cream. You'll need a little over ½ of a .11 ounce packet of powdered instant coffee. (These packets of instant coffee are my first choice for this type of recipe and I can usually find them in grocery stores for less than $5 a box.)