"Cream" without the guilt?

I've been using plain yogurt lately as a substitute for cream in pasta sauces and find it really likable. The tangy flavor makes it more like sour cream than sweet cream, but in a vegetable-based pasta dish that works well.
I made the following recipe without meat or shrimp, but it would be easy to add extra protein -- including some kind of beans or edamame -- if you wanted.

Photos show various steps: stir-frying the vegetables; after the pasta and yogurt are added to the pan; and the finished dish.

Zucchini and Red Pepper Pasta with Creamy Yogurt Sauce

Serves 4

Ingredients:

1 16-ounce package pasta shapes, such as penne or farfalle

3 T extra-virgin olive oil

1 large red bell pepper, seeded and cored and cut into 1-inch strips

2 large or 3 medium zucchini, cut lengthwise in quarters and then into 1 ½ inch strips

1 ½ cups sliced mushrooms, preferably shiitake or baby bella

3 T minced garlic

1-2 shallots, peeled and minced

Salt and pepper, to taste

1 teaspoon dried oregano, or 1 T minced fresh oregano

2 T fresh lemon juice

2 cups cooked shrimp or chicken (optional)

2 cups plain nonfat or lowfat yogurt

1 cup grated Parmesan cheese, plus more at the table

¼ cup toasted pine nuts, or a mixture of nuts such as pine nuts, slivered almonds and pumpkin seeds

Instructions:

1. Cook pasta according to package directions until al dente, drain and keep warm
2. Heat oil in a large skillet over medium-high heat. Add next five ingredients (pepper through shallots) and stir-fry for 5 minutes, until vegetables begin to tenderize and brown. Add salt and pepper and reduce heat to medium.
3. Stir in oregano, lemon juice and shrimp or chicken, if using. Cover and cook for another 2 minutes to heat thoroughly.
4. Remove pan from heat and add reserved pasta, stirring well. Stir in yogurt and one cup of cheese.
5. Divide into serving dishes or bowls, sprinkle with nuts and pass extra cheese at the table.