Help! Croissants flat and dry inside

Hi, what a shame. At least you didn't get a soggy mess which was my problem until I discovered the importance of 82% fat butter.

Here's what we need to know. What were your ingredients? How many turns did you give the laminate. How did you shape the croissants? How long did they prove? And at what temperature? Ditto for the bake duration and oven temp.

Looking at your ingredients, I have two suggestions. Did you make sure the sea salt was either fine ground or dissolved? It has to be so to be effective. Coarse crystals are a no-no. And is the chilled butter a minimum of 82% butterfat? It's hard to make croissants without it. I know from experience it can be tough work sourcing 82% butter in the States (I'm guessing from your measurements that's where you are from) but it's worth persevering.

Flat croissants suggests either not enough lamination or delamination. The latter happens when the butter becomes too warm and melts, or when the temperature difference between dough and butter is too great (really cold butter breaks up and your layers become little butter islands in a sea of dough). 

Crunchy and dry texture suggests you simply cooked them too long in the hope they would rise. We've all done that.

Concentrating your efforts on getting good lamination should do the trick. I do four turns (at least one of them a double) and they come out well (as long as I keep the dough chilled until shaping). Some chefs, for example, Michel Roux Sr. (and Jr.), recommend six turns. It's worth experimenting with both styles until you find a method that suits you.

Finally, there are some excellent videos that can walk you through the process. Check out chef Bruno Albouz's guide.

http://www.brunoskitchen.net/bread/croissant-taste-of-paris.html

(scroll down to the bottom of the page for the video)

Bruno is, as he says, the real deal, and he keeps it clear and simple whilst explaining, for example, the different kinds of turn. Much better to watch than to puzzle it out from the printed page. It's the kind of masterclass that would cost you hundreds of Euros in Paris.

Anyway, good luck and remember that everyone struggles with croissants at first. Also don't be afraid to try simpler recipes (for example, one without the milk).

In the beginning, for the longest time, my croissants always came out like that: flat, crunchy, dry interior, and bready texture instead of the flaky texture. I couldn't figure out why. Finally I figured out it was the shaggy, moist, soft dough, bulk fermentation, thick butter layers, not enough proofing time, and flouring too much during lamination. 

At the start of making the dough, add the milk and water gradually to the dry ingredients. Don't dump all the liquids in, or you'll get a soft wet dough. Knead to incorporate the ingredients. It will take a while for the flour to absorb the liquid, so knead first then wait to see if the dough needs any more liquids. Knead a bit so you get a smooth ball of dough that isn't sticky. Wrap in plastic and chill in the fridge for 5 minutes. Don't let it ferment before lamination. 

Laminate. During the rolling, don't flour excessively. Too much flour trapped in the layers creates crunchy tough layers. A light dusting of flour is all you need to prevent the dough from sticking to the counter. Brush off excess flour. Make sure the thickness of the dough is about 3 to 4 mm. You want thin sheets of butter, or you'll end up with butter pooling during the baking. If too much butter melts out during the baking, the excess butter ends up frying the croissants, and you'll end up with greasy crunchy croissants.  

Proof until they are puffy. Proofing can actually take longer than 2 hours. It could take 3 hours. 

Baking. I preheat the oven at a high temperature, around 475 F. Once they're in the oven, I lower the temperature to 425 F and bake for 5 minutes and then lower to 400 F and bake. Then after 5 minutes, I lower to 375 or 350 F and bake for the rest of the 15 or 20 minutes. If they're not thoroughly baked at the interior, they end up being flat and soggy in the center and collapse when cooled. So make sure they're thoroughly baked. They should be light when you lift them once they're cooled. 

equal amounts of flour and butter so 500g of flour would have 500 g of very cold butter instead of 300g to laminate.  You can always brush off the excess flour as you fold over to laminate.