In pressure cooker, saute bacon for 2 minutes. Add butter, onions and parsley. Saute 2 minutes, stirring.
Stir in chicken, carrot, tortellini,mushrooms (optional) and tarragon. Add broth and mix well. Secure lid. Over high heat, develop steam to high pressure. Reduce heat and maintain pressure and cook for 6 minutes. Release pressure and remove lid.
Stir in asparagus. Over high heat, develop steam to med-high pressure and cook for 2 more minutes. Release pressure and remove lid.
Combine milk, butter, 1/3 cup cheese in a bowl and blend thoroughly. Gradually add to chicken and tortellini mixture, gently stirring over medium heat until sauce thickens and becomes creamy.
Transfer to a serving platter and sprinkle with additional cheese.