Day 1: Prepare the Dough
Optional: Make strawberry milk by blending milk and fresh strawberries.
Mix the dough (détrempe) by adding flour, sugar, salt, milk (or strawberry milk), sourdough starter, water, food coloring, crushed freeze-dried strawberries, and optional yeast in a stand mixer. Mix on low, add butter, and continue mixing until smooth.
Make dark pink dough by adding more food coloring to a portion of the dough.
First rise: Let both doughs rise at room temperature for 3-6 hours, then refrigerate overnight (~12 hours).
Make the butter block: Beat butter into a square shape using parchment paper, then refrigerate.
Day 2: Laminating the Dough
Prepare dough for laminating by rolling it into a square and freezing for 20 minutes.
Roll dough, lock in the butter, and perform the first turn (book fold). Rest dough in the freezer and refrigerate for 1 hour.
Perform a simple turn to create more layers, refrigerate for 1 hour.
Add the red dough layer on top of the pink dough, roll out to a large rectangle, and refrigerate overnight.
Day 3: Shaping and Baking
Slice the dough into rectangles, then cut each rectangle into triangles. Roll each triangle into croissants.
Proof the croissants at room temperature or with steam for 2-6 hours.
Preheat oven, egg wash the croissants, and bake at 375°F for 15-30 minutes until golden brown.
Optional: Fill croissants with strawberry pastry cream.