1. Put the cream in a saucepan over a medium heat and add the condensed milk, vanilla pod and seeds, sugar and salt. Bring to a simmer, stirring to dissolve the sugar, then turn off the heat and leave to infuse for 10 minutes. Remove the vanilla pod.
2. Pour half of the infused cream mix into another saucepan and add the espresso beans and cocoa powder. Bring to a simmer, whisking to combine, then set to one side for 20 minutes to allow the flavours to infuse. Strain into a jug and then return to a clean saucepan.
3. Divide the powdered gelatine into two separate bowls and add half of the water to one of the bowls. Allow to sit for 5 minutes, then place the bowl sitting over a saucepan of simmering water and allow the gelatine to melt.
4. Whisk gently into the vanilla cream, then pour into a measuring jug. Cover with cling film and chill for about 20 minutes until just beginning to set.
5. Meanwhile, dissolve the remaining gelatine and water as before and then whisk into the espresso cream. Pour into a separate measuring jug, then cover with cling film and chill for about 20 minutes.
6. Pour about a quarter of the vanilla cream into 6-8 x 225ml glasses or similar and cover with cling film. Stick the glasses in the freezer for about 5 minutes until the layer is just set.
7. As soon as the vanilla cream is set, pour over a layer of the coffee cream – you decide how thick or thin you want the layers. Return to the freezer again for 5 minutes until set and then repeat the layers with the rest of the vanilla and espresso cream. If you find that either mix is setting too quickly in the jugs just leave them at room temperature. Return to the fridge for at least an hour.
8. To make the final espresso layer, stir the sugar into the espresso until dissolved. Meanwhile, put the gelatine and water into a bowl and set aside for 5 minutes, then set over a saucepan of simmering water and allow the gelatine to melt. Stir into the espresso and leave until cool but still pourable. Pour a thin layer over each Panna cotta and return to the fridge for another hour or so until set.
9. Serve the Panna cottas on small plates with a spoon and decorate with the chocolate covered espresso beans or a sprinkling of espresso instant powder.