Sprinkle the gelatine over the water and let it stay for 5-10 minutes.
In a heatproof bowl combine cream, milk, honey and lemon zest. Place the bowl over a pan of gently shimmering water. Whisk the mixture until the honey is completely dissolved: it should be very warm but not boiling. Add the bloomed gelatine and whisk until dissolved.
Pour the panna cotta into small jars or glasses, filling them about 2/3 full. Cover with lids or plastic wrap. Let cool in the fridge for 2-3 hours or until firm. Before serving top with blueberry jam.
If you want to make the blueberry jam on your own, simply combine 200 g fresh blueberries with 100 g sugar and few drops of lemon juice in a saucepan over medium heat. Stir continuously 20-30 minutes, until the jam reaches the desired thickness.