Sprinkle the gelatin over the cold water in a small bowl and let it bloom for 5 minutes. Set six 6 oz glasses on a tray.----------------
In a saucepan, heat 2 cups heavy cream, the almond milk, 1/3 cup allulose, 1 tsp vanilla and salt over medium heat until steaming but not boiling. Remove from heat and whisk in the bloomed gelatin until fully dissolved.----------------
Pour half of the mixture into a measuring cup and divide it between the glasses for the vanilla layer. Refrigerate for 45 minutes until just set. Whisk the espresso powder into the remaining half and leave at room temperature.----------------
Once the vanilla layer is set, gently pour the espresso mixture over the back of a spoon into each glass so it does not break through. Refrigerate for at least 4 hours until firm.----------------
For the caramel, melt the butter with 1/4 cup allulose in a small saucepan over medium heat, stirring, until deep amber, about 4 to 5 minutes. Carefully whisk in 1/3 cup heavy cream, 1/2 tsp vanilla and a pinch of salt, simmer 1 minute, then cool to room temperature.----------------
Before serving, whip 1/2 cup heavy cream with the powdered allulose until soft peaks form.----------------
Spoon a layer of caramel over each panna cotta, top with a swirl of whipped cream and a light dusting of cocoa powder. Serve chilled.