Activate the Yeast:

• In a small bowl, combine warm water, warm milk, and sugar. Sprinkle the yeast on top and let it sit for 5–10 minutes until foamy.

Prepare the Dough:

• In a large mixing bowl, combine whole-grain flour, all-purpose flour, and salt. Gradually mix in the yeast mixture and olive oil (or butter). Knead the dough for 8–10 minutes until smooth and elastic.
• Cover the dough with a damp cloth and let it rise in a warm place for 1–1.5 hours, or until doubled in size.

Prepare the Butter Layer:

• Place the softened butter between two sheets of parchment paper. Roll it into a thin rectangle and refrigerate until firm but pliable.

Laminate the Dough:

• Roll out the dough into a large rectangle. Place the chilled butter layer in the center and fold the dough over it like an envelope.
• Roll out the dough and fold it into thirds (like a letter). Chill for 30 minutes. Repeat this rolling and folding process 3 more times, chilling between each fold.

Shape the Croissants:

• Roll out the laminated dough into a large rectangle (about ¼ inch thick). Cut triangles, roll them tightly into crescent shapes, and place them on a baking sheet lined with parchment paper.

Final Proof:

• Cover the shaped croissants with a damp cloth and let them rise for 1–2 hours until puffy.

Bake:

• Preheat the oven to 375°F (190°C). Brush the croissants with egg wash for a golden finish (optional).
• Bake for 15–20 minutes, or until golden brown and flaky.