Step 1

Cook macaroni according to package directions. Drain and set aside.

Step 2

Meanwhile, melt butter in a large pot over medium heat. Add flour and mustard and whisk for 2 minutes. Gradually add broth, stirring constantly. Bring to a boil.

Step 3

Add squash and return to a boil. Stir in half-and-half and bring to a simmer. Add cream cheese, whisking constantly until it is melted. Remove from heat.

Step 4

Combine Cheddar and cornstarch in a medium bowl, tossing to coat evenly. Slowly add the cheese to the soup, stirring constantly until melted. Stir in the macaroni, vinegar and pepper. Top with chives, if desired.