Meanwhile, in 10-inch nonstick skillet, melt 2 tablespoons butter over medium-high heat. Add onion, mushrooms, thyme, salt and pepper; cook and stir 4 to 5 minutes or until tender. Stir in flour until well combined. Slowly add milk, and heat to simmering, stirring to prevent lumps. Add chicken stock, Worcestershire sauce, sour cream, cream cheese spread and poppy seed; simmer 3 to 5 minutes, stirring frequently, until slightly thickened.