Soak 2g gelatine leaf in cold water for 5 minutes.
Zest one blood orange, and use your fingers to rub the zest together with the 30g sugar for the panna cotta - set aside.
Meanwhile, juice the two oranges to yield approximately 150ml and combine with 1 tbsp sugar and gently heat in a saucepan until the sugar has dissolved.
Remove the pan from the heat, then add the softened gelatine to the blood orange juice mixture and stir to dissolve.
Strain through a sieve and into four ramekins or moulds - then chill for a couple of hours until set.
It's important to set the jelly before adding the panna cotta layer to ensure clean layers.
Panna cotta
While it’s setting, you can make the panna cotta itself - combine the milk, cream, blood orange zest/sugar mixture and vanilla to a saucepan and gently heat until it’s just starting to boil, then turn the heat off and allow the mixture to steep for 5 minutes.
While it’s steeping, soak 4g gelatine leaf in cold water to soften.
Squeeze out excess water from the gelatin leaf then add directly to the hot milk mixture – stir until dissolved.
Strain the liquid into a bowl set over a larger bowl filled with iced water, stirring frequently over 15 minutes until it cools and thickens slightly.
You must cool the panna cotta before adding it to the jelly layer to avoid melting the jelly.
Pour into the ramekins with the blood orange jelly, and refrigerate for 4-6 hours.
To serve, use a knife to gently and carefully pull the panna cotta away from the mould and break any air seal, then invert the mould onto a plate. You can use a blow torch to help release the panna cotta, or alternatively briefly submerge the base of the mould in hot water before inverting onto a plate.