In a tall container add the luke warm water and the spinach. Using an immersion blender puree everything.
Combine the green water with the yeast. Stir and let it rest few minutes.
In a stand mixer add the green mix + oil + sugar + half flour. Let the stand mixer work at low speed for 3 min.
Add salt and slowly the remaining flour.
Let the mixer work for 12 min at low speed. You will obtain a soft and quite sticky dough.
Grease your hands with some oil and remove the dough from the stand mixer. Place the dough in a bowl previously greased with olive oil, cover with plastic paper and let it rest 20 min.
Important: cover with plastic or the surface of the dough will dry out.
You will see that the dough will raise almost doubling its size.
Gently remove the dough from the bowl. Fold the dough on itself very gently few times and shape it like a sausage.
Wrap in plastic paper greased with olive oil. Cover with a cloth and let it rest for 60min. The dough will double its size again.
Remove the cloth and gently remove part of the plastic. I didn’t remove it all at once as I didn’t want the dough to dry out on the surface.
Cut a 1/2 inch slice of the dough. It will look like a small cylinder.
Roll it in semolina flour.
With your fingers gently stretch the cylinder and place it on a baking sheet greased with some olive oil.
The best baking sheet is the one with holes as it will let the air cook the grissini evenly on each side making them nice and crispy.
Bake in preheated oven to 400F for 11/12 min.
Store the grissini on the countertop in a basket simply covered with a cotton cloth for up to 1 week.