In a small bowl or measuring cup, whisk together the milk and flour until smooth. Set aside.
½ cup milk, ¼ cup all-purpose flour
Heat a medium saucepan over low-medium heat. Melt the butter in the pan, then add the onions. Stir the onions every couple of minutes until they begin to caramelize and brown slightly.
1 tablespoon unsalted butter, ½ cup white onion
After the onions caramelize a bit, add the broth, garlic powder, paprika, salt, and pepper. Stir to combine, and allow the broth to come to a simmer.
¾ cup low sodium vegetable broth, ⅛ teaspoon garlic powder, ⅛ teaspoon smoked paprika, Salt and pepper
When the broth begins to simmer, pour in the milk and flour mixture and stir constantly until the soup thickens, about 3 to 5 minutes.
Use the soup in place of canned cream of onion soup in casseroles or other dishes. Store in the refrigerator for up to 4 days until ready to use.
Notes
The calories listed are an approximation based on the total recipe. Since it is intended to be used as a full substitute for canned soup, individual serving sizes were not calculated. Actual calories will vary.The soup can be stored in your fridge, in a sealed container, for up to 4 days.