1 cup grapefruit juice (preferably from pink or red grapefruit)
2/3 cup Sugar
4 large egg yolks
4 tablespoons unsalted butter (1/2 stick, cut into 8 pieces)
  Grated zest of 1 grapefruit
3/4 cup chilled heavy (whipping) c ream
1/2 teaspoon vanilla extract
6 Fresh mint sprigs (as garnish, optional)
  berry sauce (for serving)