Sourdough Croissants

Gather the ingredients.

In a large bowl, sift the all-purpose flour, bread flour, and rye flour, if using.

To the bowl of a stand mixer fitted with the paddle attachment, add the active sourdough starter, whole milk, 1 cup of the flour mixture, and sugar. Mix on low, creating a thick dough. Scrape the paddle and the sides of the bowl, cover, and allow to rest for 30 minutes.

Fit the mixer with the dough hook and add the salt and remaining flour mixture to the dough. Mix on medium for 3 to 5 minutes, scraping down the sides of the bowl when necessary. The dough should clear the sides of the bowl and feel sticky to the touch.

Transfer the dough to a large oiled bowl. Flip to coat the dough in oil. Set aside to rest for 30 minutes in a warm place covered with a damp kitchen towel.

After resting, stretch and fold the dough by carefully picking up one side of the dough and folding it to the center. Repeat with the other three sides of the dough and flip so the seam side is down. Set aside to rest another 30 minutes.

Repeat the stretching and folding and set aside to rest for an hour. Continue this process every 60 minutes for the next two hours for a total of four folding sessions.

After the final stretch and fold, allow to continue resting until the dough is lively, elastic, and at least doubled in size. This could take up to 5 hours.  At this point, you can cover the dough in plastic wrap and store it overnight in the refrigerator, or continue to shaping.

While the dough is fermenting, prepare the butter. Shape the softened, room-temperature butter into a 5-inch-by-5-inch square and place at the center of a large piece of parchment paper.

Wrap the the parchment paper around the butter and place in the refrigerator to chill.

Once the dough has nearly doubled in size, remove the butter and allow to warm only until it become malleable, but is still cool and firm, about 30 minutes.

Turn the dough out onto a lightly floured surface and roll out to an 8-inch-by-8-inch rounded square. Using your rolling pin, roll the edges out another 2 inches, leaving the center thicker than the edges.

Place the butter into the center of the dough and fold the flaps so they overlap and enclose the butter. Pinch the edges together to seal the seams together. You should now have a square that measures close to 6 inches by 6 inches. Place the dough on a parchment-lined and floured baking sheet and refrigerate for 15 minutes.

Remove from the refrigerator and roll the dough into an 8-inch-by-16-inch rectangle. Take your time to roll gently and evenly so the dough does not split and the butter remains between the dough layers.

Situate the dough so the long side is facing you and brush the surface lightly with ice water. Fold the right 1/3 of the dough towards the center and then fold the left 1/3 of the dough over the top, enclosing the dough like a letter. This is your first turn. Return to the parchment-lined baking sheet and refrigerate for 20 minutes.

Remove the dough from the refrigerator and situate the dough so the long side is horizontal and the open edge is facing you. Roll the dough to an 8-inch-by-16-inch rectangle and repeat the letter fold technique. Return to the baking sheet and refrigerte for 20 minutes.

Repeat two more turns, rolling out and folding like a letter, brushing with ice water as needed, and chilling after each turn. Return the dough to the refrigerator for 2 hours.

Line 2 baking sheets with parchment paper or silicone baking mats. Roll the chilled dough into a 24-inch-by-16-inch rectangle.

Starting from the left, measure along the top edge of the dough and make a mark at 2 inches. Using a pizza cutter or sharp knife, cut diagonally from that mark to the bottom left edge of the dough, cutting off a triangle-shaped piece and leaving the remaining dough in a trapezoid shape. Reserve triangular piece of dough.

Working from left to right, measure and mark 2-inch increments along the top edge of the dough. Do the same along the bottom edge. Because of the trapezoidal shape of the dough, the top marks should align with the center space between the bottom marks.

Starting from the upper-left edge, cut diagonally to the first mark along the bottom edge, cutting a triangle-shaped piece of dough. Reserve. Next, cut from the new bottom-left edge to the first mark along the top edge, creating another triangle-shaped piece of dough. Continue using this method to cut out triangle-shaped pieces of dough until you use up all of the dough.

To form the croissants, hold the wide edge of the triangle and roll tightly toward the pointed edge, very gently stretching the width as you roll.

Set each roll of dough on a parchment-lined baking sheet about 3 inches apart. Cover with a damp cloth and allow to rise until about 50 percent larger.

Whisk the egg with a tablespoon of water. Preheat the oven to 400 F and brush the proofed croissants with the egg wash. Bake croissants until they are golden brown, about 18 to 22 minutes.