Step 1

Into a large pot over medium-high heat, add the butter. When the butter is melted, add the onions. Cook, stirring frequently for 2 minutes, until softened and fragrant.

Step 2

Add garlic and continue cooking for an additional 30 seconds.

Step 3

Whisk in the flour until incorporated; the mixture will be thick.

Step 4

Gradually add the broth, whisking until the consistency is smooth.

Step 5

Bring just to a boil then reduce the heat to low.

Step 6

Into the pot, add the cream cheese, cheddar cheese, milk, and black pepper. Stir frequently until cheeses are melted.

Step 7

Add the prepared mac and cheese, stirring to distribute throughout the soup.

Step 8

Adjust seasoning to taste and serve hot.