Preheat oven to 400°F.

Pam spray a casserole dish (square or round).

Alternate slices of potato and onion, forming stacks.

Place the stacks in your pan, gently pressing down to form a row of layers.

Sprinkle the potatoes with salt and pepper, and a bit of Mrs. Dash. Hold the potatoes apart to get the salt and pepper inbetween.

In a medium sized sauce pan, melt the butter.

Add the flour to make a roux.

Add the seasonings and milk, whisking until smooth.

Add the cheeses and whisk until smooth.

Pour over the potatoes, letting it get inbetween the slices.

Give a light sprinkling of parmesan cheese.

Cover with tinfoil and bake for one hour.

Remove the foil and bake for an additional 30 minutes.