Step 1: Sauté Onion and Garlic
In a large pot or Dutch oven, melt the butter over medium heat. Add the diced onion and sauté for about 3-4 minutes until softened and translucent. Stir in the minced garlic and cook for an additional minute until fragrant.

Step 2: Add Chicken Broth and Potatoes
Pour in the chicken broth and bring to a gentle boil. Add the diced potatoes and let them cook for about 10-12 minutes or until they are fork-tender.

Step 3: Introduce Chicken and Ham
Once the potatoes are tender, add the shredded chicken and diced ham to the pot. Stir well to combine all ingredients.

Step 4: Create the Creamy Base
In a small bowl, whisk together the flour and milk until smooth. Pour this mixture into the pot, stirring constantly to avoid lumps. Allow the soup to simmer and thicken for about 5 minutes.

Step 5: Add Cream and Cheese
Reduce the heat to low. Stir in the heavy cream, shredded Swiss cheese, Dijon mustard, and dried thyme. Continue stirring until the cheese is fully melted and the soup is creamy and smooth.

Step 6: Add Spinach (Optional)
If using, add the baby spinach and let it wilt for 1-2 minutes. Season the soup with salt, black pepper, and lemon juice to taste.

Step 7: Final Touches
Remove the soup from heat. Stir in the sour cream to add a tangy creaminess to the broth. Adjust seasoning if needed.