Preheat the stove to 200 degrees.
For the profiteroles, heat the water with the butter, salt, and slit vanilla bean. When the water boils, remove the vanilla bean and add the flour in one go. Stir vigorously with a wooden spoon! The flour should mix with the water to form a stable dough that comes away from the side of the pot and clings to the spoon like a clot. A whitish coating should form on the bottom of the pot.
Pour the dough into a suitable bowl, cool slightly and add the egg yolks, one by one, in great detail. Add the next egg yolk only when the previous one is completely incorporated.
Transfer the dough to a piping bag and pipe nut-sized rosettes onto parchment paper. Bake for 10 minutes until golden. Cool on a wire rack.
Beat egg yolks with half the sugar, until light and creamy. Fold in the yogurt. Add the milk, double cream and the remaining sugar. Gradually stir the hot mixture into the egg and yogurt cream. Mix in the lemon zest. Pour into an oven-proof baking dish and bake in the oven at 90 °C for 45 minutes.
Cool and refrigerate.
Stir the lemon cream well once and then fill into the slit profiteroles.
Tip: Use a normal or light yogurt as needed!