Take butter and grease a square-shaped baking dish of 8 inches and drizzle some cocoa powder over it, discard the excess.
Prepare the oven by preheating it at 350 degrees F.
Take a medium saucepan and heat some water, filled one third, and bring to a light boil.
Take a glass bowl and add chocolate, espresso powder, and butter. Keep that bowl in the saucepan. Turn down the heat flame.
Keep the bowl in the saucepan until chocolate melts thoroughly for at least 5 minutes. Blend it nicely and stream sugar in it. Blend it well till the sugar gets dissolved completely, once again, do the process.
Take out the bowl from the saucepan, put aside.
The spinach squeezes away the water from it for blending and mix the vanilla, also one tablespoon of water.
Prepare a puree of it and mix beaten eggs into it.
Until it is combined, fold in the mixture gently.
Afterwards, take a bowl and add flour, salt, cocoa powder, and baking powder. Now using a spatula, combine the dry ingredients with the dry one.
Now take the baking pan and stream the mixture onto it and bake it till it is thoroughly cooked, for 25 minutes, make sure it is a little bit moist.
Make sure the spinach brownies are thoroughly cooked before cooking.