Steam or boil the veggies until soft enough to mash with a fork. Drain and set aside. You should have 2 cups total.
Boil water and add 1.5 cups of dry macaroni. Cook to package instructions.
While pasta cooks, add the 2 cups veggie and ½ cup broth to a blender. If it’s not loose enough, add some water. Blend until smooth.
Make a roux: in a separate sauce pan on low, add 1 tbsp of butter. Once it’s melted, sprinkle in 1 tbsp of flour. Whisk constantly, and cook until it’s bubbling, 2 min.
Raise the heat to medium. One splash at a time, add in ½ cup of milk, constantly whisking. Cook until combined and bubbling, 3-5 min.
Slowly pour in the blended veggie mix into the roux. Stir continually, and cook until combined and hot.
Turn off the heat. Slowly add in the shredded cheese, stirring and melting it in as you go.
Combine the drained pasta and the sauce, and mix. Done!