For the spinach mat, remove the stems from the spinach and wash. Place in blender, adding enough water to the blender to process everything well. Blend until the spinach is chopped as small as possible.
Then pass the finely chopped spinach through a fine sieve. Discard any remaining scraps in the strainer.
Place the spinach mixture in very large pot. Bring the spinach water to a boil and let it stand until it boils. Then remove the pot from the heat immediately!
The spinach water will foam up very quickly during this process and the pot will overflow. The boiling has caused the green color to settle on top of the liquid.
Skim off the green foam with a sieve and use this so-called spinach mat for coloring pasta or spaetzle dough, soups as well as sauces.