My little guy loves Mac'n'Cheese. I am guilty of doing the box at times when I don't have time but it really doesn't take very long. I started by cutting up cubes of cheedar cheese (I used a half block of cheese) and boiling the noodles al dente, meaning not completley done, still a tiny bit hard. I used one bag of noodles.
Then I put 3 tablespoons of butter into a pan and melted it. Once the butter melted I added 4 tablespoons of flour to the melted butter.
It will look something like the above. Then you will add 2 cups of milk to this and turn the heat up so that the mixture is bubbling.
It should look like the above now. Now you can add your cubed cheese to this.
Now you can wait until all that cheese has melted, and throw in your pasta right into the pan with all the mix you just made. Once it gets gooey and cheesy, go ahead and put it into a greased casserole dish or something similar and bake at 350 for about 35 minutes.