This recipe never gets old. Plus, there are so many ways to tweak it — by varying the seasonings, the cheeses, the potato variety, etc.!
Technically speaking, scallop potatoes don’t have cheese — just a cream sauce — while Au gratin potatoes have cheese as well as cream sauce. Both can have an optional bread crumb topping — or not.
Basically, you need:
3 to 4 lbs potatoes, thin sliced (approximately 1/8 inch thick)
1/4 to 1 cup diced onion (yellow, sweet, white, purple/red, green)
seasonings of choice and quantity to taste
1 cup Parmesan cheese plus 1 to 3 cups shredded or grated cheese or cheeses of choice (for Au gratin)
4 Tbsp butter
approximately 1 to 2 cups of homemade cream sauce
a spray oiled or buttered 13 x 9 casserole baking dish
bread crumbs, optional
You can choose any kind of potatoes (peeled or not), any kind of onion, any seasonings.
Red and Yukon Gold tend to be firmer and less likely to fall apart. Russet potatoes are more tender and may fall apart easily so you have be careful not to over bake them.
Seasonings may be as simple as just adding salt and pepper or adding any (fresh or dried) herbs and spices desired.
Commonly used herbs and spices include but are not limited to: parsley, thyme, cumin, red pepper flakes, rosemary, garlic, paprika, celery seed, dill weed, basil, oregano, and cayenne pepper.
The sauce can be made with any milk, cream, or half n half plus you can add sour cream or ranch dressing if desired, as well as add any kind of broth if desired either to thin it down a little or simply add another layer of flavor. You simply want a thick, creamy sauce that is neither too thick nor too thin.
Those with lactose intolerance can whisk corn starch into a non-dairy milk to thicken it by warming the milk in a saucepan on the stove top or in microwave the non-dairy to heat it up (but not boiling or the cornstarch will just clump) and then whisk in the cornstarch. Start with 1 to 2 tsp cornstarch and give it a minute or two then if needed add additional cornstarch to reach desired thickness. You should actually stop just prior to the actual desired thickness because while baking the potato starch is going to help to thicken it a bit more.
Many will go through multiple steps of melting butter and making sauce on the stove top, will saute the onions, etc. but I just toss it together the way it was done by my family.
Most worry the onion won’t cook in time, or that the milk or cream will “break” so they like to preheat it slowly on the stove top until warm (but not boiling) before adding to the potatoes to avoid having a watery sauce with possible curdles.
If you wish to do this then by all means go for it. To avoid extra dishes, I recommend melting the butter, saute the onions, remove it from the heat to cool down a bit so it won’t curdle the milk or cream when added, to help cool it further add optional broth, then when it is cooled just add the milk or cream and seasonings to that and slowly warm it up. Don’t let it boil.
However, it is going to warm up in the oven and come to a boil anyway when being baked. The key to preventing it from breaking (separating and curdling) is bringing up the temperature slowly.
Our family recipe does bake at a lower temperature for a longer period than most recipes call for and room temperature dairy. Perhaps, that is why my family recipe works without all the extra steps.
If using the stove top method, when its ready for the oven, bake it at 350 F to 425 F degrees covered just until the potatoes are tender (about 45 to 60 minutes) then uncover to brown the top.
It may actually take longer to reach the desired tenderness depending upon just how tender you want the potatoes, variations in oven temperatures, altitude, how thick they are sliced, how deeply they are layered in the dish, how tightly packed the potatoes are, as well as the type and quantity of potatoes. If you use a lot of cream sauce, they may even cook faster due to the fact that they are boiling more so than they are baking.
Tam’s Scallop Potatoes & Au Gratin Potatoes
3 to 4 lbs potatoes, thin sliced (approximately 1/8 inch thick)
1/4 to 1/2 cup chopped green onion
4 Tbsp unsalted butter plus additional to grease baking dish
1 cup Parmesan cheese (if making Au Gratin Potatoes)
1/2 cup grated extra sharp cheddar (if making Au Gratin Potatoes)
1/2 cup shredded mozzarella (if making Au Gratin Potatoes)
1/2 cup heavy cream, room temperature
1/4 cup canned evaporated milk, room temperature
1/8 cup sour cream, room temperature
1/8 cup ranch dressing, room temperature (I use my own homemade but you can just use purchased)
1/4 tsp each: rosemary, thyme, parsley, garlic, dill weed, ground black pepper
1/2 tsp salt
paprika, plus additional dill weed and green onion (to sprinkle decoratively on top)
4 slices crispy bacon, crumbled
Note: We don’t use a bread crumb topping but you may if desired.
Butter 13 x 9 casserole dish. Dot the bottom evenly spaced with 4 Tbsp butter. (I slice into thin pats and then quarter the pats for more coverage). Set aside.
In large mixing bowl, whisk sauce ingredients and seasonings together. Taste test and adjust seasonings as needed.
Add thinly sliced potatoes and toss to coat. If more sauce is needed, just add additional cream and toss well.
If making Au Gratin Potatoes, alternate with layers of potatoes and then cheese in prepared baking dish for two or more layers of each finishing with a cheese topping. Pour any remaining sauce on top of the last potato layer prior to adding final cheese layer.
For Scallop Potatoes, simply spoon or pour the potatoes and sauce into the prepared casserole dish.
If you use bread crumbs (or cracker crumbs), sprinkle on top.
Sprinkle top decoratively with paprika, dill weed, and green onion. Set aside and preheat oven.
Preheat oven to 325 F degrees.
When oven is preheated, cover dish and bake covered for 65 to 90 minutes or until potatoes are tender.
Uncover and increase oven temp to 425 F degrees to brown top. Watch closely.
Remove from oven and allow to rest for five to ten minutes.
Top with bacon crumbles and serve.
Refrigerate leftovers, covered, for up to 3 days.
Family favorite variation/twist:
Brown up some ground Italian sausage, breakfast pork sausage, or seasoned ground beef. May also slice or dice up sausage links (no need to brown).
Cover bottom of dish with the browned meat or sliced/diced link and top with the potatoes in the usual fashion or actually toss the browned meat or sliced/diced link along with the potatoes in the sauce.
With this variation the potatoes become the main course rather than a side dish. Serve with a fresh garden salad.