Put the flour in a larger bowl and make a hole in the middle. In the depth we put the egg, sugar, salt, yeast, a little water and mix. Let the yeast "grow" for 15 minutes. Then slowly pour the warm water and knead an elastic and non-sticky dough. At the end, add the oil on the edge and knead until it is incorporated into the dough.
Then leave the dough to rise until it doubles in volume.
After doubling its volume, divide the dough into 3 equal parts. We line the table with flour. We take each piece of dough and make it into a ball. Spread each ball with the rolling pin, then cut the piece of dough into 8 equal triangles. On the wide side we put a teaspoon of finetti, then roll carefully. Let the croissants rest on the table for 20 minutes.
Beat the egg with the milk.
Wallpaper a tray with baking paper and a little oil, then place the croissants.
Grease the croissants with egg, and then put them in the preheated oven until they brown nicely on the sole.
They are delicious with a glass of milk, or anything else you want!