This is the recipe I used (I halved it though, and so everything in the recipe is on a smaller scale and done by hand). It has a lot of steps, but I've put it in here to remond me how to go about making these guys again.
Note: To make the beurrage, you beat the butter (with a rolling pin - usually a French one) between two pieces of parchment paper into a rectangle that is around 10mm (1cm) thick. I really should have some diagrams for this but I hope the photo's help!
Straight Dough Croissants
Full Recipe (I used half this makes a ton of croissants!)
4Lb 8oz bread flour
8oz granulated sugar
2oz fresh yeast (or 40% dry yeast - saf yeast?)
2.5Lb butter (for beurrage block)
Heat milk to 80F and dissolve the yeast in the milk. Pour in the bottom of a 20 quart mixer.
Add flour, then salt and sugar.
Using a dough hook mix at first speed. Wait 3 min and see if all the flour has been picked up off the bottom. If not, add water.
Dough should be a little lumpy, you don’t want to over mix.
Flour a large bowl and round the dough and place in the bowl. Cover with plastic wrap.
Leave at room temp for 1 hour.
Make the beurrage (either sheet it between two silpats into a rectangle at 10mm, or about the size of a 1/2 sheet pan). Refrigerate.
Roll out the dough by hand so that it will fit the beurrage block in the center with the two sides of dough covering the butter like a door.
Place the beurrage in the center. Fold the flaps over so they meet in the middle of the beurrage.
Seal the edges with pressure from the rolling pin, as well as sealing the center the same way.
Sheet the dough with the middle closure parallel to the sheeter. Sheet until you can do a simple tri-fold on the dough.
Refrigerate 30 min.
Repeat step 4, but face the open end of the sandwich towards you (make sure to flour the bottom of the sheeter to prevent sticking and stretching).
Final sheet to 3mm thick (make sure to do width first, then length).
Use (see pictures below for croissant shapeing. Make sure to roll to 3mm thick, and each triangle should weigh 2.5 oz).