
In a large pot, add olive oil over medium heat. Add onion and mushrooms. Cook, stirring occasionally until onions become translucent and mix becomes juicy. Approximately 10 minutes. Stir in garlic and cook approximately 3 minutes.
Add chicken stock, 1½ cups milk, thyme, parsley, salt, and pepper. Bring to a boil then reduce to low heat.
In a separate pan over medium heat, add remaining butter. Once butter is fully melted, add flour and whisk until fully incorporated. Slowly add remaining milk and whisk until fully incorporated. Add to pot.
Simmer soup on low heat for 10-15 minutes.
Serve with Parmesan sprinkled on top.