This recipe isn't an exact science. So you can add more or less of the potatoes/ham/sauce depending on how many you're feeding. But for a family of 6 this is what I do:
Par boil 5 potatoes (that means boil them but take them out a few minutes before they are tender--partially cooked through) Cut the potatoes into bite size chunks.
Buy a small ham or use left over ham or buy a thick slice of ham. Cut it up into bite size chunks.
Put the potatoes and ham in a 9 x 13 casserole dish.
Melt 4 Tb. butter in a saute pan. Once it starts to bubble add 4 Tb. of flour. Slowly whisk in 2 cups of milk (you may need more or a bit less--you just want a nice saucy thickness). Add salt and pepper and dry mustard to desired flavor. It should be a nice tasting sauce. Pour over the potatoes and ham and gently fold in to cover all in the pan.
Cover dish in tin foil and bake at 325 for 1 1/2 hours. Add cheese on top at the end. Enjoy!!!
My entire family loves this meal! Hope you enjoy!