8-10 medium potatoes (Russet or Yukon Gold are best)
1/4 cup cold butter, cut into small squares
2 Tbsp. flour
2 cups shredded cheddar cheese, divided (old or medium cheddar is best)
2 cups milk
1 tsp. coarse salt
1 tsp. dried mustard or paprika
Wash, peel and thinly slice potatoes.
Butter 9 x 13 casserole dish.
Layer 1/3 potatoes, 1/3 butter, 1 tbsp. flour and 1/3 cheese.
Repeat (potatoes, butter, flour, cheese).
Follow with final layer of potatoes and top with remaining 1/3 butter.
In bowl mix milk, salt and mustard and pour over top of potatoes.
Cover with tin foil and bake in preheated 350F oven for 1 – 1.5 hours until potatoes are soft and bubbly.
Sprinkle with remaining cheese and bake uncovered for another 15-20 minutes.