Fill a large pot with 4 quarts of water. Add 2 tablespoons of the olive oil and 1 teaspoon salt. 

Cover and bring water to a boil. Add the pasta and cook according to the instructions.

Drain pasta, reserving some of the cooking water.

Heat the olive oil in a large frying pan and sauté the chicken strips for 10 minutes.

Add the onion and garlic. Sauté for 5-7 minutes more, or until the onion is soft, stirring occasionally.

Stir in the mushrooms, oregano, pepper, and remaining 1/2 teaspoon of salt. Cover and cook for 10 more minutes, adding a little more olive oil if necessary.

Add the creme fraiche or cream to the skillet, stir well, and simmer, covered for another 5-8 minutes. 

Remove from heat, add the spinach, and cover for 3 minutes. This will soften the spinach a bit and keep it fresh and green.

Stir the cooked pasta into the sauce and stir well. Adjust salt and pepper if necessary.

Serve with Parmesan cheese and fresh parsley.