To do the day before:
Vanilla ice yogurt:
Put the yogurt in a small strainer covered with a coffee filter and refrigerate for a few hours.
Recover 2 cups (500g) of drained yogurt, add the milk, sugar, and grated vanilla, and mix well.
Churn in an ice cream maker.
Grapefruit granité:
Mix the juice and sugar well and put in the freezer until completely set.
Marmalade:
Make a few incisions in the grapefruit, then put it in a saucepan and cover with cold water. Bring to a boil.
Remove the grapefruit from the water and repeat the process three more times.
Cut the grapefruit into quarters, add the sugar, and cover with water.
Cook over low heat for a few hours, until the grapefruit is well-cooked.
Let it cool overnight in the refrigerator, then finely chop.
To do on the same day:
Yogurt crepes:
In a bowl, mix the egg yolks and yogurt with a whisk.
Add the flour and mix well.
Beat the egg whites and mix with the sugar.
Fold this meringue into the yogurt mixture. Refrigerate.
Marinated grapefruits:
Peel the grapefruits and carefully remove the membranes.
Squeeze and save the remaining juice from the membranes in a saucepan, add the water, sugar, grated vanilla, and bring to a boil.
Pour the hot syrup over the membranes and refrigerate.
Assembly:
In a non-stick pan, heat a little butter and cook the crepes.
When they are lightly colored, flip them over and finish cooking for 2-3 minutes in the oven at 350F (180C).
In a small bowl, put a few marinated grapefruit membranes.
Using a fork, form crystals with the granité, which you will place on the membranes.
Finish this assembly with a scoop of vanilla ice yogurt.
Serve the crepes with the marmalade.