Place 1 cup instant nonfat dry milk in a 1-liter mason jar with a tight-fitting lid.
Add cornstarch, bouillon powder, minced onion, parsley, and pepper. Screw the lid on and shake until evenly combined.
Add remaining cup dry milk. Screw the lid back on and shake again. Store in a cool, dark pantry until ready to use.
To use: When a recipe calls for 1 can of condensed cream of soup, add ⅓ cup dry mix to a small saucepan. Whisk in 1 cup cold water.
Place saucepan over medium high heat. Cook for 5 minutes, whisking constantly. Remove from heat; set aside for 5 minutes to cool and thicken. Use as you would for a recipe that calls for one can of soup.