Cook the pasta according to the instructions on the package. Drain pasta and set aside.
Steam the broccoli and cauliflower by using a steam basket or microwave. Steam the vegetables until they are very tender (about 8-10 minutes).
Add the milk, broccoli, and cauliflower in a blender. Blend until smooth.
Melt the butter on medium heat in a saucepot. Add the flour to create a roux or thickening paste. Whisk the flour and the butter together to create a paste and until it has a nutty fragrance. It should not get too brown.
Whisk in the “green milk” and stir very well until it starts to thicken.
Allow the mixture to simmer gently and season with the nutmeg and black pepper.
Gently stir in the shredded cheese.
Transfer the macaroni to a large bowl. Pour the cheese mixture over the noodles and stir to evenly coat.
You can now serve the macaroni and cheese just like this or you can add panko bread crumbs to the top for an added crunch (for the big kids and adults).