Begin by zesting one orange using a fine grater, ensuring you only take the bright orange part, discarding the white pith.

Slice the orange in half and squeeze out the juice into a measuring cup, straining it to remove any pulp or seeds.

Set aside the hollow orange halves for serving later.

In a medium saucepan, combine heavy cream, sugar, orange zest, and optional vanilla extract.

Heat gently over medium-low heat for about 5 to 7 minutes, stirring consistently, until the sugar dissolves and the mixture begins to thicken slightly.

Remove the saucepan from the heat and gradually stir in the strained orange juice.

Carefully pour the creamy mixture into the prepared orange halves, filling them generously.

Let the orange shells sit at room temperature for 10 to 15 minutes, allowing the mixture to settle and cool slightly.

Transfer your filled orange halves to the refrigerator and chill for at least 4 hours, or ideally overnight.

When ready to enjoy, remove the posset from the refrigerator and serve chilled in their vibrant shells.