Place a saucepan with the milk on the heat, pour in the zest of a lemon and bring to the boil;
Take a bowl, pour in the egg yolks, add the sugar and whisk;
Add the starch and mix, then pour in two ladles of boiling milk and mix everything together:
Then pour the egg mixture into the remaining milk and whisk until the cream is thick;
Turn off, pour into a bowl, cover with cling film and leave to cool;
Let’s prepare the dough:
Melt the butter in a bain-marie and warm the milk;
On the work surface, arrange the flour in a fountain shape and add: the sugar, the crumbled yeast, the eggs, the melted butter and the lukewarm milk. Add the salt to the sides (be careful not to touch the yeast);
Using a fork, begin to mix all the ingredients;
Knead vigorously for about 15 minutes, using the flour as a support, until you obtain a smooth, homogeneous dough (you can also use a planetary mixer);
Form a loaf, cover with a cloth and let it rise for about 2 hours, it should double in volume, in the oven turned off with only the light on;
Once ready, deflate it and divide it into 3 well-rolled cylinders, each approximately 18 cm long;
Shape the braid, seal the sides well, place on a baking tray lined with baking paper, cover and leave to rise for another hour;
Brush the surface with the egg yolk, now fill the folds of the braid with the help of a piping bag, with the custard, add the sugar grains and cook at 180 (pre-heated oven) degrees for 25/30 minutes;