Preheat oven to 375°F and prepare biscuits on a baking sheet according to package directions. Start baking them about 10 minutes after you begin the soup. Heat 1 tablespoon olive oil and 1 tablespoon butter in a 5-6 quart pot or Dutch oven over medium-high heat until butter melts and shimmers.

Add diced onion and sliced celery with about 1/4 teaspoon each salt and pepper. Cook, stirring frequently, for about 8 minutes until softened and onion is translucent with golden edges.

Reduce heat to medium. Add minced garlic, thyme, oregano, and sage with salt and pepper. Stir constantly for 30-45 seconds until fragrant, watching carefully so garlic doesn't burn.

Create a well in the center of the pot and add remaining 4 tablespoons butter. Let melt, then add frozen vegetables with salt and pepper. Cook for 2 minutes, stirring frequently as vegetables begin to thaw.

Sprinkle flour over everything and stir continuously for 1 minute to cook out the raw flour taste. Mixture will look paste-like and coat your spoon.

Add 1/4 to 1/2 cup chicken broth to deglaze the pan, scraping all browned bits from the bottom with a wooden spoon until the pan looks clean.

Gradually whisk in remaining chicken broth and heavy cream until smooth and lump-free. Add shredded chicken and bring to a simmer over medium-high heat, stirring occasionally.

Reduce heat to medium-low and simmer uncovered for 3-5 minutes, stirring occasionally, until chicken is heated through and soup reaches desired thickness (should coat the back of a spoon). Taste and adjust seasoning with additional salt and pepper. Serve with warm biscuits and garnish with fresh parsley.