1/3 C warm water
1½ T active dry yeast
2 T + ½ tsp sugar
2 C flour
1 tsp salt
¼ C + 1 T cream
1½ T melted unsalted butter
¾ C very cold butter
1 egg yolk
Directions
In a small bowl combine warm water, yeast and ½ tsp sugar; let stand until foamy (about 5 minutes).
In bowl of stand mixer, combine flour, 2 T sugar and salt in a bowl, set aside.
Add melted butter and ¼ C cream to yeast mixture. With stand mixer on low speed, add yeast & butter mixture to dry ingredients. Increase spead to medium-low and knead dough utnil smooth and elastic (6-8 minutes). Dough will remain slightly tacky.
Shape dough into ball; wrap in plastic wrap. Refrigerate overnight (or at least 8 hours).
Unwrap chilled dough. Working on a lightly floured surface, roll dough to ½" thick rectangle (approx 8x12"). Layer with butter, folding and rolling to laminate in many layers. Refrigerate an hour between foldings and rollings as needed to make sure the butter stays cold.
There are various methods here for layering/laminating the butter into the dough. Some pound and flatten the butter into a ¼" thick rectangle (about 8x4") laying it in the center of the dough so the 8" length of butter spans the 8" width of the dough, then folding the 4 inches of dough from either side over the butter. Others grate the very cold butter -- can even be frozen -- using a cheese grater and sprinkle the butter between layers of dough, alternating folding and rolling between adding additional layers. The purpose is to create layers of dough and butter that will bake into the flakey layers traditional with croissants. I've not yet experimented enough to say which is my personal preferred method.
Refrigerate dough 1 hour after last folding/lamination.
Line 1-2 baking sheets with parchment paper.
Roll dough to a rectangle approximately 12x18". Using a sharp knife (or pizza cutter) cut dough into 6-8 triangles 3-4 inches at the base, 12" tall (see picture). Roll each croissant from base to tip; shape, if desired, into a crescent and place on parchment lined baking sheet.*
*If you want to make pain au chocolat (chocolate croissants), they are traditionally rectangular pieces of dough rolled around 'bars' of chocolate.
In a small bowl, combine egg yolk with 1 T cream; brush croissants with mixture.
Proof croissants by placing the baking sheet of croissants in a cold/off oven; boil 2 cups of water, place the bowl of boiling water in the bottom of the oven. Close the door. Let croissants proof 2-4 hours until doubled in size.
Remove croissants from oven (and remove the bowl of water). Preheat oven to 425° F.
Brush croissants with a second layer of egg-cream mixture. Place in middle rack of oven and immediately reduce heat to 375° F. Bake until deep golden brown (25-30 minutes).