Setting the Build: In a small clean glass jar, thoroughly combine the 7g of ripe starter culture, 35g of flour, and 35g of water. Seal loosely and allow to ferment at room temperature (74–78°F) for 10 to 12 hours overnight until it safely reaches its absolute peak before mixing.

Yeast Activation & Incorporation: In your stand mixer bowl, whisk together the 74g of water, 64g of milk, and 3g of instant yeast. Stir in the 60g of active overnight hybrid starter, 34g of sugar, and all 230g of bread flour.

Mechanical Gluten Mixing: Attach the dough hook and begin mixing on medium speed for 2 minutes until a shaggy mass forms. Add the 5g of fine sea salt and continue mixing. Drop in the 11g of softened unsalted butter and knead continuously for 5 to 6 minutes until the dough comes together tightly. If the mass remains overly sticky, add 20 to 30g of extra flour until it cleans the bowl sides.

Intermittent Stretch Cycles: Transfer the dough to a clean container. Cover and let it rest for 30 minutes. Perform your first round of stretches and folds. Cover, let rest for another 30 minutes, and perform a second round of stretches and folds to optimize structural vertical strength.

Dual-Temperature Thermal Stabilization: Wrap the smooth dough tightly in plastic wrap. Transfer it directly into the freezer for 30 minutes to rapidly arrest yeast activity, then move it into the refrigerator to chill slowly for 2 full hours.

Butter Block Calibration: While the dough chills, place your 140g of cold pastry butter between sheets of parchment paper. Roll it firmly into a neat square measuring roughly 10cm on each side. Chill the block in the refrigerator for 30 minutes before laminating. The butter must be cold yet pliable—if too stiff, it will fracture; if too warm, it will smear.

Enclosing the Core: Remove the cold dough from the refrigerator. Roll it out into a clean rectangle measuring roughly 25 x 15 cm. Place the chilled pliable butter block squarely in the center and fold the dough flaps over it securely to encase the fat entirely.

The Book Fold Sequence: Gently roll the enclosed block lengthwise, pushing the internal butter smoothly from one side to the other. Trim away any irregular uneven edges. Fold the extended dough sheet cleanly like a book (a four-layer fold).

The Letter Fold Sequence: Rotate the dough pack exactly 90 degrees. Roll it out lengthwise a second time. Trim any rough edges and fold the sheet into thirds like a standard letter (a three-layer fold). Wrap the laminated packet tightly in plastic wrap and chill in the refrigerator for 1 full hour to relax the gluten network.

Final Sheet Extension: Remove the rested packet from the fridge. Roll the dough out carefully into a uniform square measuring roughly 23 to 25 cm on each side, maintaining an even thickness of 4 to 5 mm throughout.

Triangle Partitioning: Using a sharp pizza cutter or chef's knife, cleanly slice the dough square into elongated triangles. Ensure the base of each individual croissant triangle measures exactly 8cm in width.

Tension Rolling: Starting at the wide 8cm base, roll the dough triangle up gently yet tightly toward the narrow point to form a traditional layered croissant shape. Arrange the shaped pastries onto a parchment-lined baking sheet.

The Jiggly Ambient Proof: Cover the tray loosely with plastic wrap. Let the croissants proof undisturbed at room temperature for 4 to 5 hours. They are fully proofed when they have completely doubled in volume, show highly visible delicate layers, and wobble like jelly when the baking sheet is gently shaken.

Flash Heat Preheat: Thoroughly preheat your oven to 425°F (220°C). In a small bowl, whisk together the 1 large egg and 2 tablespoons of water until completely smooth. Tenderly brush a thin layer of the egg wash over the curved crowns of each swollen croissant, ensuring it doesn't pool in the laminated layers.

The Structured Bake: Slide the tray onto the middle oven rack. Bake at 425°F (220°C) for exactly 10 minutes to trigger maximum oven spring and crisp the outer shell. Without opening the door, immediately turn the oven temperature setting down to 375°F (190°C) and bake for an additional 15 minutes until the croissants are beautifully golden brown. Cool on a wire rack before shattering open.