Make espresso coffee and leave it to cool down.

Soak the sheets of leaf gelatin in a medium bowl with cool water for 10 minutes until they soften.

In a medium saucepan, combine the cream, sugar and vanilla. Place the pan over medium heat and stir gently until the sugar dissolves. Heat the mixture until it reaches the scalding point, without allowing it to boil (around 70-80°C if using a kitchen thermometer).

Remove the pan from the heat. Retrieve the softened gelatin sheets from the water and gently squeeze out any excess water. Add the gelatin to the cream mixture, stirring until completely dissolved.

Stir in the espresso coffee. Then let the panna cotta mixture cool for 15-20 minutes at room temperature, giving it an occasional stir.

Pour the cream mixture to a pouring jug. Carefully divide the panna cotta mixture among 4 serving glasses (use dessert cups, custard cups, wine glasses or martini glasses), ensuring it doesn't spill down the sides. Leave the glasses at room temperature until the panna cotta cools down completely.

Cover the glasses with plastic wrap and refrigerate for at least 6 hours or until the panna cotta sets. It should still maintain a delightful wobble when gently shaken.

To make the sauce, place chocolate double cream and espresso in a bowl set over the simmering pot of water, making sure the bottom of the bowl doesn't touch the water (like a double boiler). Stir until the chocolate melts.