Add all dough ingredients to a stand-mixer fit with a dough hook attachment. Mix on low for 3 minutes. Then, turn the speed to medium and knead for 3 minutes. Once combined and kneaded, remove from bowl and form a round ball. Place on a large, floured plate and cover with plastic wrap. Not too tight or the dough won't grow, but not too loosely or it will dry out. Refrigerate overnight or for at least 8 hours.
The next day, cut a large piece of parchment paper and place it on your work surface. Grab the cold, unsalted butter to prepare the butter layer. Cut the butter length-wise into 1/2 inch slabs.
Arrange the pieces on top of the parchment paper in the shape of a square about 5 1/2 inches x 5 1/2 inches, cutting the butter, as necessary, to fit. Place any cut pieces on top of the square. Place a second piece of parchment paper on top of the bottom so that the butter is in between the two pieces of parchment.
Using your rolling pin, slowly, yet firmly, roll out the square so it is now 7 1/2 x 7 1/2 inches. Trim any edges so they are straight and place trimmings on top. Pound them in with the rolling pin. Refrigerate the butter layer while you roll out the dough.
Grab chilled dough from the refrigerator and unwrap it. Flour your work surface so the dough does not stick. Place dough on surface. Roll dough out to a 10 1/2 inch square. Brush off excess flour.
Grab butter from the refrigerator. It should be pliable but cold. Refrigerate longer if needed. Unwrap and place butter in the center of the square, with each point of the butter square in the middle of each edge of the dough. The dough should look like a square and the butter layer will resemble a diamond-shape. Fold one flap over the butter towards you until the dough reaches the center of the butter layer. Repeat with other three flaps so that the butter is fully enveloped in the dough. Seal the edges so the butter won't escape when we roll it out.
Now we will roll out the dough to begin creating the layers. Lightly flour the top and bottom of the dough. Using the rolling pin, press firmly on the dough and begin elongating it. Focus on lengthening it instead of widening it. Soon, the butter and dough layers will begin to combine and it will be easier to roll out. Roll until the long side is 24 inches and the short side is 8 inches. Now, fold one of the short ends about 1/3 of the way. Fold the other side over the first folded side so that the dough resembles a folded letter. Put the dough back on the floured plate and completely cover with plastic wrap (no edges exposed to air). Freeze for 20 minutes to relax the dough.
Remove chilled dough from freezer. Repeat rolling and folding process from the previous step, but this time, roll in the direction of the open ends. Freeze another 20 minutes. Repeat one last time. Place folded dough back on floured plate and into the refrigerator overnight or at least 8 hours.
The next day, remove the dough from the refrigerator. Lightly flour your work surface. Place dough on work surface. Roll into the direction of the open ends, focusing on lengthening. Roll out until the dough is 8 x 44 inches. If the dough begins to get sticky (especially on the bottom), sprinkle it with flour.
Once it's the desired length, trim off 2 inches from the ends to make them completely straight. The dough should now be 8 x 40 inches. Discard trimmed dough.
Lay a yardstick or measuring tap along the top of the rectangle of dough. Using a paring knife or pizza cutter, make a small cut in the dough every 5 inches. You should have 7 cuts. Then, place the yardstick or measuring tape at the bottom of the dough. Make a cut at the 2 1/2 inch mark. Now, make a cut every 5 inches from that nick. You should have 8 cuts that fall halfway between the marks on the top of the dough rectangle.
Make a diagonal cut from the first top mark to the first bottom mark using a pizza cutter. Now, do the same for the first bottom mark to the second top mark. Repeat for the remaining marks until you have 15 triangles. They should resemble isosceles triangles, for my math friends.
Prep two baking sheets with parchment paper. Now we are ready to form the croissants. If you find that the bottom of the dough is sticky, use a paring knife to scrap it off the surface and flip it over. You want to make sure you smoothest side is facing out ward once the croissants are shaped. That means, you need to have the smooth side on the bottom and rougher side on top.
Cut a 1/2 inch slit in the middle of the shortest side of the triangle. This will help give the croissants their shape. Pull on the point directly across from this slit to stretch the dough to 10 inches long. Starting with the short side, roll the dough towards the pointed end until the pointed end is on the bottom of the croissant. Slightly bend the ends of the croissant towards the middle to resemble a crescent. You can press the ends together if you want a distinct crescent shape but I always leave them not touching. Repeat with remaining croissants.
Place rolled croissants on baking sheet so they are 2 inches apart. They will rise during proofing and also while baking so don't let them touch.
Prepare egg wash by scrambling a raw egg with 1 teaspoon of water. Brush all croissants with the egg wash. This will give them their color and sheen. Refrigerate excess wash, as you will use it again. Let them proof in a draft-free spot. I always put them in my oven or a cupboard. They will need about 1 1/2 - 2 hours to rise. They will be jiggly and their layers will show when they are ready to bake.
When there is about 20 minutes left for the croissants to finish proofing, turn on the oven to 425 degrees. Make sure the rack is in the bottom half of the oven.
When they are done proofing, brush again with egg wash. Bake for 10 minutes in a preheated oven. Rotate and bake for an additional 8 minutes until deep golden brown. Let them cool for 10 minutes until eating. Serve with your favorite jam or preserves.