Combine the yeast, milk, bread flour, cake flour, salt, sugar, cold water, and butter. Knead using a stand mixer on low speed for about 5 minutes, then increase to high speed and continue kneading for 15–20 minutes until the dough is smooth and no longer sticks to the bowl.
Roll the croissant dough into a flat sheet approximately 30 × 60 cm. Cover tightly with plastic wrap and refrigerate for 30–45 minutes.
Roll the croissant butter (1 kg) into a 30 × 30 cm square. Place the butter sheet onto the rolled dough, cover with plastic wrap, and refrigerate for about 30 minutes. The butter and dough should both be at approximately 5–6°C for easier lamination.
Roll the dough into a sheet about 30 cm long and fold using a single fold (letter fold). Rest in the refrigerator for 30 minutes.
Roll and fold the dough again using a double fold (book fold). Rest for 90 minutes.
Using a sharp knife, cut the laminated dough lengthwise into even strips, about 1 cm thick. Stack the strips onto the uncut portion of the dough and gently press to adhere. Lightly roll with a rolling pin—do not apply too much pressure to avoid damaging the layers. Roll the dough to a thickness of 3–4 mm, then cut into shapes (base 10 cm, length 30 cm). Roll from the base and place into triangle molds as shown.
Proof for about 2 hours at 26°C. Bake at 200°C for approximately 18 minutes.
