Roasted Vegetable Potato Au Gratin Casserole
A hearty casserole combining creamy potato au gratin with roasted root vegetables for added nutrition and flavor. Colorful turnips, beets, and carrots are roasted until caramelized, then nestled into a rich cheese sauce made from convenient boxed potato mix. The vegetables add natural sweetness and vibrant color while maintaining their tender texture. Perfect as a satisfying side dish for family dinners, holiday meals, or potluck gatherings. This version transforms the classic comfort food into a more wholesome dish without sacrificing the beloved creamy, cheesy appeal that makes au gratin potatoes so popular.
Ingredients
- 1 tablespoon extra-virgin olive oil
- 2 small turnips, peeled and dicedparsnips1:1flavor
similar sweetness and texture
- 2 small beets, dicedsweet potatoes1:1colorflavor
maintains vibrant color
- 2 small carrots, sliced into 1-inch pieces
- 1 box (4.9 oz) Betty Crocker Potato Mix Au Gratin
- 2 cups boiling water
- ½ cup milk
- 2 tablespoons butter
- ¼ cup parsley, chopped
- 1 pinch coarse salt and freshly ground pepper
Instructions
- 1
Preheat oven to 450°F
- 2
Toss diced vegetables on rimmed baking sheet with oil and season with salt and pepper
- 3
Roast vegetables 30 minutes, flipping halfway through
- 4
Remove vegetables from oven and set aside
- 5
Combine water, milk, butter, potatoes and cheese packet in 2-quart baking dish and whisk
- 6
Bake 10 minutes
- 7
Remove from oven and sprinkle roasted vegetables over gratin, nestling into sauce
- 8
Return to oven for 15 to 20 more minutes until top is browned and bubbly
- 9
Garnish with fresh parsley and serve
Tips
Cut vegetables into similar sizes for even cooking and roasting
Nestle roasted vegetables gently into the sauce to prevent breaking the creamy texture
Let the casserole rest 5 minutes after baking for easier serving and better texture
Good to Know
Cover and refrigerate up to 3 days, reheat in 350°F oven
Assemble up to 1 day ahead, cover and refrigerate, add 10 minutes to final baking time
Serve hot as side dish, let rest 5 minutes before serving for easier portioning
Common Mistakes
Cut vegetables uniformly to avoid uneven cooking
Don't skip flipping vegetables to prevent burning
Nestle vegetables gently to avoid breaking the creamy sauce
Substitutions
use 2 lbs potatoes with cheese sauce
similar sweetness and texture
FAQ
Can I use fresh potatoes instead of the boxed mix?
Yes, use 2 pounds thinly sliced potatoes layered with cheese sauce made from butter, flour, milk, and cheese for a homemade version.
What if my vegetables aren't tender after 30 minutes?
Continue roasting in 5-minute intervals until fork-tender, as vegetable size and oven variations can affect cooking time.
How long will leftovers keep in the refrigerator?
Properly stored leftovers will keep for 3-4 days in the refrigerator and reheat well in the oven or microwave.