Bring 3 quarts of water to a boil. Place a bowl filled with water and ice next to the stove top. Plunge the spinach into the boiling water and blanch for 1 minute. Remove from the boiling water with a slotted spoon and immerse in the ice water. When cooled, remove from the water, squeeze in a towel to dry and place in the bowl of a food processor. Puree until a very fine paste forms.
Mound 3 1/2 cups of the flour in the center of a large wooden cutting board. Make a well in the middle of the flour and add the egg and spinach and the olive oil. Using a fork, beat together the eggs and oil and begin to incorporate the flour, starting with the inner rim of the well.
As you expand the well, keep pushing the flour up from the base of the mound to retain the well shape. The dough will come together when half of the flour is incorporated.
Start kneading the dough with both hands, using the palms of your hands. Once you have a cohesive mass, remove the dough from the board and scrape up and discard any leftover bits. Lightly re-flour the board and continue kneading for six more minutes. The dough should be elastic and a little sticky. Wrap the dough in plastic and allow to rest for 30 minutes at room temperature. Roll out to the thinnest setting on a pasta rolling machine. Cut the pasta into 1/4-inch wide ribbons, place on a sheet tray that has been liberally sprinkled with semolina flour, cover with clean towels and set aside.