Heat the olive oil in a large Dutch oven over medium heat.
Add the onion, carrots, and celery. Cook for 7 to 8 minutes, stirring occasionally, until the vegetables begin to soften.
Add the garlic, sage, thyme, smoked paprika, and nutmeg. Cook for 30 seconds, stirring constantly.
Add the pumpkin puree and chicken broth. Stir until the pumpkin is mixed into the broth.
Increase the heat to medium-high. Bring the soup to a gentle boil.
Reduce the heat to medium-low. Simmer uncovered for 15 minutes, or until the vegetables are tender. Remove from the heat.
Using an immersion blender, blend the soup until smooth. Return the Dutch oven to low heat.
Add the shredded chicken and milk. Cook for 5 minutes, stirring occasionally, until the chicken is heated through. Do not let the soup boil.
Place the Greek yogurt in a medium bowl. Slowly add ½ cup of the hot soup to the yogurt while whisking until smooth.
Remove the Dutch oven from the heat.
Stir the yogurt mixture into the soup. Add the lemon juice, salt, and ground black pepper. Mix well.
Notes
Serving Size: 1½ Cups
Tips and Tricks
Use plain pumpkin puree - Check the can before adding it. Pumpkin pie filling contains added sugar and spices that will change the soup.Temper the Greek yogurt - Mixing hot soup into the yogurt before adding it to the Dutch oven helps keep the yogurt smooth.Keep the heat low after adding dairy - High heat can cause milk and Greek yogurt to separate.Adjust the thickness after blending - If the soup becomes thicker than you prefer, stir in a small amount of chicken broth or milk.
Storing and Reheating
Refrigerate - Store leftover soup in a covered container in the refrigerator for up to 3 to 4 days.Freeze - Dairy-based soups can change texture after freezing, so freezing is not the preferred storage method. If frozen, stir the soup well while reheating.Reheat on Stovetop - Place the soup in a saucepan and warm over low to medium-low heat, stirring occasionally. Do not let it boil.Reheat in Microwave - Place one serving in a microwave-safe bowl. Heat in short intervals, stirring between each interval, until heated through.