1) Turn oven on to 350°. Fill a large pot 1/2 full of water. Add 1 t. salt to the water. Put it on the stove and turn the flame on high.
2) Grate 2 cups of cheese. Measure it in the large glass measuring cup.
3) Get out the largest frying pan. Cut a cube of butter in half. Unwrap one half and put it in the pan. Put the other half back in the refrigerator. Turn the heat on low and slowly stir the butter around the pan until it has all melted. TURN THE HEAT OFF!!!
4) About this time the water in the large pot should be boiling. Put 2 cups of macaroni into the water and stir to break up the clumps. Set the timer for 8 minutes and 30 seconds. When timer goes off, drain macaroni right away. If you wait, it will get mushy.
5) After the heat is off under the butter--measure 1/4 cup of flour using one of the plastic yellow measure cups. Pour it into the pan with the butter. Mix the flour and the butter together with a whisk until it is smooth without lumps.
6) Using the other large glass measuring cup to measure 1 2/3 cups milk.
7) Turn the heat to on to medium under the butter and flour. Pour the milk in and stir constantly keeping lumps from forming. It will slowly smooth out as it heats up. Cook this mixture until it starts to thicken and boil--STIR the whole time it is cooking or else it will get yucky lumps.
8) When it gets thick and bubbly, turn off the heat and add 1/2 t. salt and 1/8 t. garlic salt. Then add the 2 cups grated cheese. Stir until all the cheese has melted. Add the cooked macaroni and mix gently with the sauce.
9) Pour into a casserole dish. Grate some more cheese on top. Put into the oven and heat at 350° for 25 minutes.