I always start by boiling the water for the pasta and cooking it. The sauce doesn't take nearly as long as as pasta!
Then I make a roux. Unfortunately, you can't just add cheese to pasta and have it come out a nice creamy mac and cheese. You have to have a sauce base. Its easy though! Just melt a tablespoon of butter in a saucepan, and then add a tablespoon of flour. Whisk it together for just a minute. If I had more time, or was making this for dinner or guests, I'd saute some diced onion in that butter. Then add in about a cup of milk. It will start to thicken as it heats. If the sauce looks too thick, add more milk. Some salt too for flavor.
2-serving Mac and Cheese
4 oz or about 1/2 cup small pasta
1 T butter
1 T flour
1 cup milk* plus extra for thinning sauce
1 cup shredded cheese
salt to taste
Cook pasta to al dente. Meanwhile, melt butter in small saucepan and then add in the flour and whisk together for just a minute. Add in the milk and whisk until thickened. Then add in the cheese and stir until melted in. Add in your pasta and seasonings and serve.
I use whole milk because that is what we use in our house. We use raw if we can get it - the less processed the better.