6 c. potatoes, 1/2" cubes
1/2 c. green onions, sliced
3/4 c. celery, finely chopped
4 tbsp. butter
4 tbsp. flour
2 tsp. salt
3 c. milk
2/3 c. mayonnaise

Cover potatoes with hot salted water. Simmer 5 minutes; drain. Place potatoes in a 13 x 9 baking dish. Sprinkle onions and celery evenly over potatoes. To make sauce, melt butter in 3-quart saucepan or skillet over medium heat. Blend in flour and salt, cook and stir until bubbly. Gradually add milk, stirring until smooth. Cook until mixture thickens. Remove from heat. Stir in mayonnaise until smooth. Pour over potatoes. Mix in carefully with fork. Smooth top. Bake at 375 degrees for 25 to 30 minutes or until bubbly. Garnish with chopped fresh parsley if desired.