Infuse the Cream: In a medium saucepan, whisk together the double cream, sugar, and orange zest. Heat gently over medium-low heat until simmering, stirring occasionally to dissolve the sugar. Don't let it boil.

Simmer and Temper: Once simmering, reduce the heat to low and let the mixture simmer gently for 5-7 minutes, stirring occasionally. Do not let it boil. Remove from heat and stir in the orange juice and Cointreau (if using).

Strain and Chill: Strain the mixture through a fine-mesh sieve into a jug or bowl. Cover and refrigerate for at least 4 hours, or preferably overnight, to allow the posset to set and thicken.

Prepare the Garnish: While the posset chills, segment the orange by slicing off the ends and the peel, then following the curves of the fruit to remove the flesh without the pith. Arrange the segments on a plate or small bowl.

Serve and Savour: When ready to serve, divide the chilled posset among individual bowls or glasses. Garnish with fresh orange segments and mint leaves for a touch of elegance. Enjoy!