Place the starter, flour, sugar, salt, egg, water, and room temp butter in a medium bowl and mix with your hands until everything is roughly incorporated and no dry flour remains.  It will be a bit shaggy at this point. That is okay.  Cover and let rest 30-60 minutes.

After the rest period is up, dump the dough onto an un-floured counter. Grab the dough by the middle and lift, then tuck the ends under itself (this video shows how). This is called folding the dough. Repeat this about 3 times or until the dough is just barely smooth and is holding together nicely. We don't want to develop the gluten too much or it will be hard to roll later. You want it just smooth enough that it's holding together nicely. When done with the folds, place in the fridge for about 2 hours.

When the dough has about 20 minutes left in the fridge cut a piece of parchment paper approximately 12"x 18". Cut the cold butter into thin slices and place in a roughly 8" x 8" square. Fold the parchment over the butter, encasing all of the butter in parchment.

Take a rolling pin and beat the butter with the pin to flatten and warm it up a smidge. Beat it until its flattened out a good amount the roll the butter to the edges of the parchment. Keep rolling the butter until it is a solid sheet of butter that is slightly pliable and is about 8" x 8". Set aside.

Take the cold dough from the fridge and place on a floured counter. Roll the dough into a square that is big enough to fold the butter block into, about 10" x 10". Place the butter block so that the corners of the butter block are at the flat sides of the dough, kind of like a diamond in a square.

Fold over the corners of the dough to meet in the middle of the butter block and completely encase the butter. Gently tap this dough with the rolling pin to secure it. Let rest for about 15 minutes.

After the rest, roll the dough to about 18" long, not making it any wider. Then fold the top down about 2/3 of the way, then fold the bottom to meet the top. Tap with the rolling pin to secure. Then fold it in half again. You'll end up with a roughly 10" x 3" rectangle of folded dough. Cover and rest for another 15 minutes. If it is warm you may need to stick it in the fridge. The dough should feel cool, not cold but not warm at all times.

After the rest is up take the dough to a floured counter again and set it so that the short side is parallel to you. Roll it longer again keeping the approximate 3" width the same, roll it long until it is about 18" again.

Fold the top down to the middle, then fold the bottom over the top so that you have a rough square of dough. Cover and rest for 15 minutes. Alternatively you can put this in the fridge until the next day but be sure to take it out of the fridge a couple of hours before you plan to roll the final croissants out.

After the rest roll the dough to 10" high and 1/4" thick, the width of the dough doesn't really matter here. Once it is 10" high and 1/4" thick cut the croissants into triangles with bases 3.5" wide. Or cut into cruffins by cutting straight strips of 2".

Then roll the triangles of dough starting with the base toward you, rolling it to the tip. Place it on a parchment lined baking sheet with the tip tucked under. For cruffins, roll the stips of dough like a cinnamon roll and place in an extra large muffin tin like this one.

Cover the shaped dough with a plastic bag (I use clean garbage bags) and leave to proof at 68*-70*f for 18-24 hours or until significantly larger (two to three times the size), with layers separating slightly and jiggly when the pan is jostled.