01 - In a small bowl, sprinkle gelatin over the grapefruit juice. Let it bloom for 5 minutes until the gelatin absorbs the liquid.
02 - In a saucepan, combine the cream, milk, sugar, vanilla extract, and grapefruit zest. Heat gently over medium heat, stirring constantly, until sugar is completely dissolved and the mixture is hot but not boiling.
03 - Remove from heat. Stir in the bloomed gelatin mixture and whisk thoroughly until fully dissolved into the hot cream base.
04 - Pour the mixture through a fine mesh sieve into a clean bowl to remove the grapefruit zest, ensuring a silky smooth texture.
05 - Pour the strained panna cotta mixture evenly into 6 ramekins or serving glasses, filling each about three-quarters full.
06 - Allow to cool to room temperature, then cover with plastic wrap and refrigerate for at least 4 hours or until completely set and firm to the touch.
07 - If desired, toss grapefruit segments with 2 tablespoons sugar and let sit for 10 minutes to macerate, enhancing their natural sweetness.
08 - Top each chilled panna cotta with macerated grapefruit segments and fresh mint leaves. Serve immediately while chilled.