Step 1

Using a small saucepan, add the heavy cream and sugar over medium-high heat, stirring constantly. Bring to a gentle boil, and boil for 3 minutes, stirring constantly. If the boiling cream is bubbling too much, turn the heat down to a medium, but maintain a gentle boil. To prevent it from boiling over, lift the saucepan off the burner for a few seconds, then return to the burner and continue stirring.

Step 2

Remove from heat and whisk in the grapefruit juice. Pour the mixture into serving dishes. Cover and chill in the refrigerator for at least 4 hours or until set.

Step 3

When ready to serve, zest one grapefruit (2 teaspoons). Mix with the sugar. Sprinkle over the posset and garnish with whipped cream (optional).