NOTES: a) If using frozen spinach, skip steps 3-5; b) if omitting the spinach, use 1 1/4 cups of flour.
Heat a skillet to medium heat, and add spinach; don't use cooking spray or oil.
Cook spinach for about 30 seconds, stirring continuously. Spinach should turn a bright green color.
Plunge spinach immediately into an ice water bath to stop the cooking process.
When spinach has cooled down to lukewarm temperature, squeeze out the excess moisture using a cheesecloth.
Add spinach, olive oil, eggs, and salt to food processor and run until fully blended.
Add flour to food processor and run until blended. If the mixture is still sticky, add flour.
Remove dough from food processor. Roll dough into a ball and wrap in plastic wrap. Allow to rest at room temperature for 20 minutes.
Transfer dough to a work surface that's generously dusted with flour. Cut dough into 4 pieces.
If using a pasta maker, roll each piece out with a rolling pin until it's about 1/4" thick. If not using a pasta maker, roll until thin and hand-cut as desired.
Shape dough into rectangles and run through pasta maker, starting with the widest setting. If the dough sticks in the rollers, dust the dough and the rollers with flour.
Continue rolling dough through the rollers, gradually reducing the setting to flatten it as desired. NOTE: spinach pasta may need to be 1 setting wider than you normally want because of the stickiness of the dough.
Cut pasta into shapes using the appropriate attachment.
Lower pasta into water (don't drop it) and boil for a few minutes. Don't crowd the pot with pasta, as this can cause pasta to stick together.
NOTE: Don't dump the whole pot of cooked pasta into a strainer the way you might with dry, boxed pasta. If transferring to a strainer, don't rinse with water.
Using tongs or a spider skimmer, remove pasta from the water and transfer to a different container. Doing it this way will help the pasta keep its shape, and allow you to use hot water for the remainder of the boil.