In a saucepan, heat the milk and the vanilla bean split in half.
While waiting for the boil, whisk the egg yolks and sugar until it whitens a little.
Once the milk has come to a boil, remove the pod, pour 1/3 into the egg yolk/sugar mixture and whisk.
Pour everything back into the pan with the milk.
Over medium heat, continuing to mix with a spatula, heat the mixture but stop there before it boils if you don't want to end up with an omelette.
The cream should coat the spatula.
For more precision, if you have a thermometer, stop cooking at 82°C.
In a saucepan, bring blueberries and sugar to a boil.
Using a hand blender, mix the whole thing and sieve to get just the liquid.
Beat the whites with a pinch of salt until they become frothy.
Add the sugar in 4 times.
Whisk until firm to obtain meringue.
In the microwave, cook the meringue at 300W for 2 minutes and 30 seconds.
The preparation should double in size.
In a saucepan, melt the isomalt powder and add the dye tip (optional)
Using a fork, make horizontal and vertical threads all over the back of a silicone half-sphere mold (beware, isomalt hardens quickly).
Allow the half-spheres to cool and gently remove by pushing the isomalt-free parts of the mould with a knife, if the domes are glued together, heat a knife blade and cut off the excess ones
If you missed or broke your shells, you can put them back in the pan, melt them and start again.
Once the half-spheres are cooled, prepare the dessert, starting with a ladle of custard, half a sphere, an ice spoon of meringue.
For extra grip, heat the underside of the 2nd sphere slightly with a blowtorch or lighter to make it stick.
Add drop of blueberry sauce around the sphere and with a toothpick form a circle through each of its drops to form hearts.
Servings 0