- Combine cream, milk, tonic syrup and sugar in a saucepan.
- Using a microplane or fine grater, remove the zest from the lemon and add to the saucepan. Heat gently on a medium heat, stirring intermittently to dissolve sugar and incorporate ingredients. Do not boil.
- Meanwhile, place some paper towel on a small flat tray and arrange and lightly grease your dariole moulds** with some spray oil, removing any excess oil with a paper towel. Ensure your moulds are sitting perfectly flat, otherwise your panna cotta will set unevenly.
- Once the sugar has dissolved and the mixture is steaming (roughly 5 mins), take the saucepan off the heat and allow to cool for 2 mins.
- Sprinkle the gelatine evenly over the top of the mixture. Allow to dissolve for 30 seconds and then stir again to ensure all the gelatine is incorporated fully.
- Strain the mixture through a fine sieve into a jug, to remove the zest and any undissolved gelatine. Then fill the moulds evenly, giving each a small tap on the bench top to remove any trapped air bubbles.
- Transfer the tray of filled moulds to the fridge and chill for a minimum of 2 hours, preferably 4. To check if they are set, select one panna cotta and tilt slightly. If the liquid moves or bulges at all, it is not set sufficiently.
- To serve, break the seal by inserting a small knife in-between the panna cotta and the mould. Turn the mould onto the serving plate and give a gentle tap to release. Serve with some orange segments, or perhaps a lemon shortbread for some textural variation.
*Meyer lemons are an heirloom variety prized by pastry chefs for their natural sweetness. You may be able to find them at farmers' markets, dependent upon the season. If you cannot find a Meyer, a regular lemon will do just as well.
** Dariole moulds are small plastic or metal cup moulds used by chefs for setting individual sweet and savoury dishes. These can be found at any good homeware or kitchen supplies shop. Ramekins or small glasses can be used as an alternative, but you may not be able to decant the final product.