This recipe is not for those who dread things that take a long time to make. But you don’t have to be a professional baker to make these! I am far from being even close to a professional baker, but making these with my sister was an interesting and enjoyable experience.  

On to the recipe!

Okay, so for your ingredients for the dough, gather:

• ¼ cup of butter (softened to room temperature) 
• 4 cups of all purpose flour (and a little extra for rolling out the dough) 
• ¼ cup of sugar.
• 2 teaspoons of salt.
• 1 tablespoon of instant yeast. 
• 1 and ½ cups of milk (whole milk is recommended but I think other kinds will do) 
• 1 bar of semi-sweet 4-ounce chocolate bar. 
• For the butter layer:
• 1 and ½ cups butter (softened to room temperature)
• 2 tablespoons of all purpose flour. 
• For the final set of ingredients, the egg wash:
• 1 large egg
• 2 tablespoons of milk (again whole milk is the recommended kind)

Wait to get the butter layer and egg wash ingredients until those steps. 

Now it is time to begin!

1. It is time to make the dough. Cut the butter into four 1-tablespoon slices and then add to the bowl of the stand mixer. (if you do not have a stand mixer then a handheld one will work or you can use no mixer) put the dough hook attachment onto the mixer and add your flour, sugar, salt, and yeast. Turn the mixer onto a low-medium speed to combine the ingredients. (let this go for a minute, making sure the ingredients are combined) next slowly pour in the milk while the mixer is running. After all the milk is added, turn the mixer up to medium speed and it will begin to knead the dough. 
2. Let the dough knead for at least 5 minutes in the mixer or, if you want, this step can be done by hand. Sprinkle a little flour on the dough if it becomes too sticky while kneading. Don’t add too much flour otherwise it will become dry. After the kneading process is finished, the dough should still be a little soft, poke it with your finger and if it slowly bounces back, the dough is ready. 
3. Take the dough out of the bowl and with lightly floured hands, make it into a ball. Line a baking sheet with parchment paper and place the dough on it. Gently flatten the dough out and cover with plastic wrap or foil and place in the fridge. Let it rest there for 30 minutes. 
4. Clean your counter and lightly flour it. Now it is time to remove your dough from the fridge and place it on the counter. Begin to flatten the dough with your hands before rolling it. Use the rolling pin to roll the dough into a 14×10 inch rectangle. Use your hands to shape the dough, until you have the correct size rectangle. 
5. Place the dough back on the tray and into the fridge for 4 (or up to 24) hours in the fridge. 
6. This next step, (the butter layer)  should be done about 35 minutes before you are taking the dough out of the fridge. In a large bowl using a handheld mixer or the stand mixer with a paddle or whisk attachment, mix the butter and flour together until it is combined and smooth. On a baking sheet with parchment, smooth the butter layer into a 7×10 inch rectangle. Then place this in the fridge for 30 minutes to chill. 
7. Now you will begin to roll the dough into a large rectangle on a lightly floured counter. Remove the butter layer from the fridge and place in the center of the dough. Even out the edges of the butter using a sharp knife. Now seal the dough edges over the butter layer as best as you can with your fingers. Begin to roll the dough into a 10×20 inch rectangle. After you have the dough into the correct size, fold it lengthwise into thirds (almost like folding a letter but with dough) If the dough is too warm to continue working with, place it back in the fridge, covered for 30 minutes to rest. 
8. Place the dough on the counter with the short end facing the direction of you. Roll the dough out again into a 10×20 inch rectangle and once again fold lengthwise into thirds. Place the covered dough back in the fridge to rest for 30 minutes. 
9. Remove the dough from the fridge and once again roll into a 10×20 inch rectangle and fold lengthwise into thirds. Now it is time for a long rest. Place the covered dough into the fridge for 4 hours (or up to 24 hours is okay.)
10. After the rest time, remove the dough from the fridge. Lightly spread flour on your counter and roll the dough out (use your fingers if you need to.) Once you have a 8×20 inch rectangle, slice the dough in half vertically. Then cut 3 even slices horizontally, making 8 rectangles sized at 4×5 inches. Then cut each rectangle in half lengthwise so that you now have 16 rectangles, all sized 2×5 inches. 
11. Now coarsely chop up your chocolate to lay on the dough. After your chocolate is chopped up, proceed to the next step. 
12. Work with one piece of dough at a time. Roll it out until it is 8 inches long. Then place a few pieces of chocolate in a layer on one end of the dough and tightly roll the dough up. Repeat until all the croissants are rolled up. Now line another baking sheet with parchment so that you have two baking sheets. Place the croissants on the two baking sheets and cover. Let these rest at room temperature for 1 hour and then place in the fridge for 1 hour. 
13. After your croissants are done resting, preheat your oven to 400 degrees Fahrenheit. Prepare your egg wash by whisking the egg and milk together. Lightly brush each croissant with the egg wash. 
14. Place the croissants in the oven until golden brown, for about 20 minutes. Rotate the pans about halfway through baking. If they begin to darken too quickly, switch the temperature to 375 degrees fahrenheit. 
15. Remove the croissants from the oven and place on a wire rack to cool. If you want, dust powdered sugar over the top before enjoying. 

Here I have included the original recipe. 

https://sallysbakingaddiction.com/homemade-chocolate-croissants/