Gently warm the milk - you can do this on the stove but easiest is in the microwave for around 20 seconds in a small microwavable bowl/custard dish. Sprinkle the gelatin over the milk and leave for around 10 - 15 minutes to bloom. The gelatin will absorb liquid and become more of a wobbly solid.
Gently warm the cream and coconut sugar in a small pan over a medium-low heat. You just want to warm the mixture enough to dissolve the sugar, but don't let the mixture boil. It should only really become warm.
Remove the cream from the heat and add the milk-gelatin mixture, the espresso, vanilla and salt. Mix everything well to combine.
Divide the mixture between two ramekins/custard dishes or glasses and chill for at least 2 hours.
Once the panna cotta has set, you can serve either in the dishes or by investing onto a plate (see notes above on how to help it come out of the dish if inverting).
Video
Notes
If you don't have coconut sugar then use muscovado or dark brown sugar.