Put the cream and the blossoms into a heavy bottomed sauce pan and stir to combine. Heat on medium stirring occasionally, until the mixture just comes to a simmer. Turn off heat and let it cool to room temperature. Cover, put in the refrigerator, and leave overnight, making sure that the flowers are immersed in the cream.
Strain the cream through a fine mesh sieve. Measure out 1 1/2 cups. (You'll have a bit leftover)
Whisk the egg yolks and sugar together in a saucepan. Add the strained cream (1 1/2 cups) and the grapefruit juice.
Heat on medium, stirring constantly, until the mixture just comes to a slight simmer and thickens. Don't boil.
Pour the thickened mixture into small glasses or cups, you should have four servings.
Refrigerate until fully chilled, or overnight.
Garnish with a blossom or a twist of grapefruit zest if you like.
https://theviewfromgreatisland.com/grapefruit-blossom-pot-de-creme/ March 2, 2016