Add 1 cup water, cover, and cook for 8-10 minutes till soft.
Carefully puree the vegetables in a blender or with a stick blender till smooth.
Season with salt, and keep aside.
Cheese Sauce
In a saucepan, melt the butter, and add flour.
Keep whisking continuously for about 2-3 minutes.
Add 1/4th (about half a cup) of milk at a time and keep stirring.
The flour will start lumping, which is expected.
Keep whisking/stirring continuously as you add all the milk.
Keep stirring/whisking till you get a thick smooth sauce that coats the back of your spoon.
Take off the heat. Add shredded cheese and stir till completely melted.
Hidden Vegetable Mac & Cheese
Add the puree to the cheesy sauce, and mix well.
Add the cooked macaroni to cheese and vegetable sauce and mix well.
Adjust seasoning and serve warm.
Notes
Prevent cheese sauce from splitting: If your white sauce (thickened butter, flour, milk misture) is too hot and bubbling away, it can split the cheese. To avoid this, turn off the heat first, and then fold in the cheese.Lumpy White Sauce: Start with warm milk. When the flour is cooked, add about half cup of warm milk and whisk vigorously. Then slowly add the remaining milk stirring continuously. If you do find lumps, simply strain it through a sieve.