Cheesy scalloped potatoes

These are the best ever scalloped potatoes and should make about 8 servings. Easiest made in a blender.

6 med potatoes, peeled and sliced
1/4 cup diced onion
1/4 cup celery leaves
2 springs parsley
3 tbsps flour
1/4 cup butter
1 1/2 tsps salt
1/4 tsp pepper
1 1/2 cups milk
1-2 cups grated old cheddar cheese

Blend everything except potatoes and cheese in blender, mixing thoroughly. Arrange potato slices in buttered 2 quart baking dish. Pour blender mixture over potatoes and sprinkle with grated cheese. Bake uncovered in 350 oven for approx 1 hour.