Homemade Butter Croissants

Place the flour in a mixing bowl and make a well. Add the sugar and salt.  

Warm the milk and crumble the yeast into it. Add a spoonful of sugar and leave for 5 minutes.  
Add this mixture to the dry mixture. Add the eggs one at a time.  

Knead the dough for ten minutes, until it is uniform and supple.  
Make a ball, cover, and leave it to rise for 1 hour, somewhere warm and dry. Once the dough has doubled in volume, degas it for a few moments to knock it down, before placing it in the refrigerator for 30 min.  

Roll out the dough on a floured work surface, making a square shape. Gently add the slightly softened butter on top.   
Fold the four corners into the center.  

Using the rolling pin, lengthen the dough to make a rectangle, taking care not to let too much of the butter escape. Repeat this process, then leave to rest in the refrigerator for 30 minutes, to firm the butter.  

Roll out the dough into a thin, even rectangle approximately 40 x 50 cm (16 x 20 inches) in size, then cut this into two halves approximately 20 cm x 50 cm (8 x 20 inches) in size.  
Make triangles measuring approximately 20 x 10 cm (8 x 4 inches).  

Roll each triangle into a small croissant shape, finishing with the ends.   
Place the croissants on a baking sheet lined with parchment. Leave to rise for 1 hour.   

Mix the egg yolk with a spoonful of water and brush the croissants with the mixture.   
Bake for 15 minutes at 210°C (410°F).