Scalloped Potatos

I recently made these for my Mom's birthday get together and they came out very well. As usual, I started with a great recipe from Allrecipes.com called "Scalloped Potatoes and Onions" and made some changes to improve the recipe. The nice part of this recipe is that it uses a velouté sauce instead of using a sauce based on milk or cream. This results in a much lighter tasting dish where the taste of the potatoes, onions and the topping can shine through.

INGREDIENTS
    5 large russet potatoes, peeled and thinly sliced
    3/4 c. finely chopped onion
    3 Tbs. butter or margarine
    1 Tbs. olive oil
    1/4 c. all-purpose flour
    1 3/4 c. chicken broth (low sodium)
    2 Tbs. mayonnaise
    3/4 tsp. salt (or to taste)
    1/8 tsp. pepper

Topping:
    1/2 c. plain bread crumbs
    1/4 c. Parmesan Cheese
    3 Tbs. Butter


DIRECTIONS
Note, using a mandolin slicer or a food processor to slice the potatoes makes life a little easier.

   1. In order to speed up the cooking process, we will begin the cooking of the potatoes in a large pot on the stove. Place the sliced potatoes in a large pot with enough water to cover the potatoes. Add a little salt to the water, but be careful not to over salt.
  
   2. Put the pot over high heat until the water just beings to boil, then back off the heat until it just barely bubbles. Cook until the potatoes are just starting to turn tender. Drain the potatoes, reserving 1 cup of the cooking liquid.
 
   3. While the potatoes cook, start making the sauce. In a saucepan, melt the butter; stir in flour until smooth and cook for a short while, do not brown it like a roux. Gradually add broth while whisking until smooth. Add the mayonnaise and whisk to combine. Cook and stir for 2 minutes or until thick and bubbly. Add salt and pepper to taste.  

   4. In a greased 2-1/2-qt. baking dish, alternate layers of potatoes and onion until they are all in the pan.
   5. Pour the prepared sauce over potatoes and make sure that it seeps down and between all the layers, you may need to use a spoon to jiggle the potatoes around a little.

   6. Cover and bake at 325 °F for 30 minutes.

   7. Melt the butter in a saute pan and then add the breadcrumbs and toss to coat. Keep the breadcrumbs on the heat until they just start to brown. Remove from heat and continue tossing until they cool down a bit. Add the Parmesan cheese and toss together.

   8. Remove the potatoes from the oven and sprinkle the topping over the top as evenly as you can. Return the potatoes to the oven and continue cooking for 30 minutes or until tender and the topping is browned.

   9. When done, allow the potatoes to cool a bit before serving.