Soak half of the gelatine in 2-3 tbsp cold water and let stay for 5-10 minutes. The gelatine should absorb the water completely and bloom.
In a heatproof bowl combine 7/8 cup milk (200 ml) and 7/8 cup cream + about half of the sugar. Add also the vanilla extract. Place the bowl over a pan with gently shimmering water (double boiler). Whisk the mixture until the sugar is completely dissolved. Add the chocolate, broken into pieces, and whisk again until dissolved. Finally add the gelatin and whisk until dissolved.
Pour the chocolate panna cotta into glasses or ramequins, half-filling them. Cover each cup with plastic wrap. Let cool in the fridge for 1-2 hours until firm.
Repeat the same procedure with the rest of the gelatine, cream, milk, sugar and rum extract. When the second batch of panna cotta is ready, pour it in the glasses/ cups of already firm first batch. Cover again with plastic wraps. Let stay in the fridge for 5-6 hours or overnight.
Depending on the type of glasses used, the panna cotta can be served in two ways which I have presented both in the pictures. If it is in high glasses, just pour some morello cherry jam on top and serve directly in the glass. If it is in ramekins, invert each panna cotta onto a serving plate and spoon over the jam.
Store the leftover panna cota for 4-5 days in the fridge.
If you don't have morello cherry jam, try with raspberry, strawberry or any other kind that is slightly sour. Alternatively you can use regular cherry or blueberry jam as well.