Remove the puff pastry from the plastic wrapper and set it on the counter to come to room temperature. DO NOT microwave.
Heat oven to 400 F. Line a baking sheet with parchment paper and set aside. Prepare a medium casserole dish by spraying with nonstick spray.
In a large skillet, add the butter and chopped onion. Heat over medium and stir to coat. Let this cook for 3 - 4 minutes until the onions start to become translucent.
Add bouillon, rosemary, pepper, salt, thyme, water, and vegetables to the onion in the pan. Stir over medium heat until the mixture comes to a boil. Reduce heat to low and simmer for 8 minutes.
Stir in chicken, cream cheese, and yogurt. Stir over low heat for about 5 minutes until almost boiling.
Pour the chicken mixture into the prepared casserole dish.
The puff pastry should now be easy to unfold and cut. Cut it into enough small rectangles for each serving bowl to be topped with pastry. Bake the pastry on the top rack and the casserole on the bottom rack for 15 minutes at 400 degrees.
After 15 minutes, the pastry should be light golden brown and the chicken mixture will be bubbling. Remove from oven. Spoon the chicken mixture into serving bowls and top with baked pastry.
Serve Creamy Chicken Pot Pie hot.