Add the instant coffee granules and hot water to a small bowl. Stir until dissolved, then let cool completely.
Pour the cold heavy cream into a large bowl. Beat until soft peaks form.
Reduce the mixer speed to low. Slowly add the sweetened condensed milk and cooled coffee concentrate.
Mix until thick, smooth, and fluffy. Do not overmix.
Fold in chocolate chips, if using.
Transfer the mixture to a freezer-safe pan or container. Smooth the surface.
Cover tightly and freeze for at least 6 hours or overnight.
Let sit at room temperature for 5 to 8 minutes before scooping.