Mix heavy cream, sugar, and salt together over low heat and whisk until thoroughly blended.
Gradually add the cream into the whisked egg yolk until combined.
Add instant coffee powder and mix until the coffee dissolves.
Turn off the heat when the mixture begins to thicken.
Strain into a clean glass container.
Let it cool to room temperature and put it in the fridge for at least four hours (preferably overnight).
Take it out and pour it into an ice cream machine to freeze before transferring it into an air-tight container; keep it in the freezer until it’s ready to serve.