Heat a large skillet, non-stick frying pan, or dutch oven with a lid on medium heat. Add a drizzle of olive oil. Once the oil is heated, add the diced onion. Saute the onion for 3-4 minutes, until it's starting to soften.
Add the minced garlic, mushrooms, thyme, and black pepper. Don't add salt yet. Cook 4-5 minutes until the mushrooms are sweating and softened. Now add the salt.
Add orzo and broth, bring to simmer. Cover and simmer for 10-12 minutes on medium to medium-low heat until orzo is al dente, stirring occasionally to prevent it from sticking to the bottom of the pan. Give it a taste and add more salt as needed. The cooking time will vary a bit based on your stovetop and type of pan. If it looks too dry, add a quarter cup more broth at a time up to half of a cup.
Turn off the heat and add the spinach, lemon juice, and parmesan cheese. Stir to combine until the spinach is wilted, about 1-2 minutes.
Add the Greek yogurt, stirring gently until it's dissolved into the pasta. Serve directly from the pan you cooked it in or in a nice pasta dish.
