• Mix the dough: In the bowl of a stand mixer, add the flour, sugar, water, milk, sourdough starter, salt, and optional active dry yeast. Use the dough hook attachment and mix on low speed for 1 minute. Add the softened butter and continue mixing, scraping down the sides as needed, until a smooth dough forms. This should take about 4 minutes. Note: do not add the chocolate chips yet.

  600 g (4 ¾ cups) all-purpose flour, 65 g (⅓ cup) granulated sugar, 12 g 2 teaspoons salt, 60 g (¼ cup) active sourdough starter 100% hydration, 205 g (1 cup) water, room temperature (34%), 112 g (½ cup) whole milk, room temperature (18.5%), 56 g (¼ cup) unsalted butter, cut into ½-inch pieces, chilled (9.5%), Optional: 1.5g (½ teaspoon) active dry yeast (0.2%)
• First rise: Transfer the dough to a bowl or container, cover, and let rise at room temperature for 3-6 hours until it reaches approximately 1.5x its original size.
• Cold proof: Once the dough has risen sufficiently, transfer it to the refrigerator to cold-proof for a minimum of 4 hours or overnight (~12 hours).
• Prepare the butter block: Start by laying out a large sheet of parchment paper. Place your sticks of butter next to each other in the center of the paper and fold the sides of the paper over to fully enclose the butter. Flip the parchment paper over so that the folds are against the table. Using a rolling pin, lightly beat the butter into a ½’’ thick layer. Remove the butter from the parchment paper and re-wrap the butter, measuring the parchment paper so that it forms an 8’’ square. The ½’’ butter layer should be smaller than the 8’’ parchment paper square. Flip the packet over again and beat the butter into an 8’’x8’’ square that fills our the parchment paper. Refer to the video linked below for helpful visual cues for this process. Eventually, it will be easy to roll the butter out to the edges of the parchment paper and get a clean square shape. Place the butter in the fridge to firm up. Video: Making the Butter Block.

  340 g (1 ½ cups) unsalted butter, 84-86% butterfat

Day 2: Laminating The Dough

• Prepare the dough for laminating:  After the dough has rested in the fridge for a minimum of 4 hours or up to twelve hours overnight, remove it from the fridge and place on a floured surface. Use your hands to deflate the dough and form it into a rough square shape. Wrap the dough in plastic wrap on all sides and use a rolling pin to roll it into a 8-inch by 8-inch square. Place the wrapped dough in the freezer for 20 minutes. Video: Preparing the Dough.
• Roll the dough: Remove the butter from the refrigerator and remove the dough from the freezer. Unwrap the dough and place it on a light floured surface. Roll the dough lengthwise into a 16-inch by 8-inch rectangle.
• Lock in the Butter: Place the butter block in the center of the dough and peel off the parchment paper. Make sure the butter is aligned with the sides of the dough with an equal amount overhanging at the top and the bottom. Fold the overhanging flaps of dough over the butter so that the two ends meet in the middle. Gently tug if necessary to bring the ends together. Seal both sides of dough together with your fingers and pinch the other sides of the dough to fully enclose the butter.  Video: Locking in the butter.
• First turn: Rotate the dough so the seam is vertical. Roll the dough, lengthwise, to create a 24’’ long sheet that is ¼’’ – ½’’ thick. With a knife or a dough cutter, trim the short ends of your rectangle so that you have a clean 24’’ long rectangle that is straight on all four sides. Take the shorter edge of the rectangle farthest from you and fold it towards the center of the dough, lining up the edges. Press down lightly to make sure the dough sticks together. Do the same with the opposite side, leaving a small ⅛’’ gap between the edges in the middle. Next, fold the entire dough in half along the 1/8'' gap, bringing the top half down over the bottom half. At this point, you should have a rectangular packet of dough, also known as a “book,” with four layers. This technique is referred to as the “first turn” or “book fold” and it quadruples the butter layers within the dough. Video: First Turn – Book Fold.
• Rest the dough: Wrap the dough tightly in plastic wrap and place in the freezer for 15 minutes, then refrigerate for 1 hour.
• Simple turn (second turn): Remove the dough from the fridge and let it sit at room temperature for about 5 minutes. Lightly flour your work surface and roll out the dough into a 24'' x 8'' rectangle again, creating a long, narrow slab about ⅜’’ thick. Fold the dough into thirds. This is called the “simple turn,” and it triples the layers in the dough. Wrap the dough again in plastic wrap and freeze for 15 minutes, then refrigerate for 1 hour. Video: Simple Turn.
• Pre-shape the dough: Using your rolling pin, roll the dough out into a 14’’ x 17’’ rectangle. Wrap and freeze for 20 minutes then refrigerate overnight, between 8-12 hours.

Day 3: Shaping and Baking the Croissants

• Slice the dough: Remove the dough from the fridge and place it on a lightly floured surface. Re-roll the dough so that it’s a 14-inch x 17-inch rectangle. Use a knife or wheel cutter to trim any uneven edges so that you have a rectangle that’s exactly 14 inches by 16 inches. Now slice the dough into four 4-inch x 14-inch rectangles. Starting with one rectangle, use a knife/wheel cutter and a ruler to slice a straight line from one corner of the rectangle to its opposite corner, creating two long, equal triangles. Repeat this process with the remaining rectangles to create 8 triangles in total. Using a knife or a wheel cutter, trim the base of your triangle to ensure it’s a nice straight line. Starting one triangle at a time, widen the base by gently tugging on the 2 corners of the bottom of the triangle. You’re looking to achieve a 3’’ base of the triangle. Then, running your fingers along the length of the triangle towards the point, gently pull to lengthen the triangle. Video: Shaping Croissants.
• Add the chocolate chips: Now it’s time to add the chocolate chips to the dough. With your triangle slices lying flat on a work surface, begin adding chocolate chips to the side that is facing up. Scatter them across the top so that they’re evenly distributed. Aim to use about half of your chocolate chips for this step, and reserve the other half for topping once the croissants have been rolled.

  30g (¼ cup) mini chocolate chips
• Roll the croissants: Working one triangle at a time, start at the base of the triangle and roll the dough towards the tip to form a crescent-shaped croissant. Repeat this process with all 8 triangles.
• Top with chocolate chips: Gently add the remaining chocolate chips to the exterior of the shaped croissants. Be careful not to press too hard, you want to get the chocolate chips to stick on without damaging the layers you’ve built. Place each shaped croissant into a baking cube.

  Note: If using the large baking cube referenced above, place three shaped croissants stacked on top of each other into each baking cubes (you will have enough to fill 2 cubes and cover. Place the remaining two croissants on a baking sheet and cover with plastic wrap – these two croissants will be baked as regular crescent shaped croissants.

  30g (¼ cup) mini chocolate chips
• Proof the croissants: There are two options for the proofing step; a room temperature proof or a faster proof using a proofing box or steam-oven technique.

  Option 1 - Room temperature proof: Let the croissants proof at room temperature for roughly 4-6 hours until they are jiggly and have roughly doubled in size.

  Option 2 – Faster proof with steam: Using a proofing box, countertop oven with a proof setting, standard oven with proof setting, or by placing a pan filled with warm water in an off oven to create steam, proof your croissants at 70F-75F for 2-3 hours until jiggly and doubled in size.
• Preheat oven and chill croissants: When your croissants are done proofing, preheat the oven to 375F and transfer the proofed croissants to the fridge to chill for 20 minutes.
• Egg wash: In a small bowl, whisk together the heavy cream and egg yolk. Remove your croissants from the fridge and use a pastry brush to apply the egg wash to the top layer of the exterior of your croissants (do not brush the exposed layers). Video: Egg wash.
• Bake the croissants: Place the cubes upside down on your baking sheet and bake the croissants for 15 minutes. Flip the cubes right side up and bake for another 10-15 minutes until nicely golden brown. Allow the croissants to cool in the baking cube for a few minutes before removing. Once you removed, allow the croissants to cool completely on a baking sheet.
• Serve and Enjoy!