Mix flour, sugar, salt, milk and yeast and knead for 5 minutes. Roll the dough into a rectangle of 20X30 cm en and leave this in the fridge for at least an hour. Get the butter out of the fridge half an hour before you will use it. Roll the butter into a rectangular of 12X17 cm (put some flour underneath to make the rolling easy). Put this in the middle of the dough and fold the dough rectangular around the butter. Roll the whole mass out again till 20X30cm. Put back in the fridge for 1 hour. Repeat the process three times. then cut triangles from the dough and make croissants. Bake them 10 minutes at 200 degrees, turn the oven down to 180 degrees and bake 15 minutes more.

We tend to think that the croissant is French, if only by the sheer abundance of those delicious rolls in France, but there are different stories going around. Some say it originated in Hungary, some say in Poland or Vienna, and all in relationship to winning a battle. Obviously there are kitchen history experts, who say the croissant came from France.
The name croissant refers to "crescent": the shape of a growing moon and that is the shape your croissant should ideally get. Dip them in a big bowl of "café au lait" like the French do for breakfast: yummy!