This easy Tuna Casserole is completely assembled and prepared in one pan -- throw uncooked pasta, tuna, and veggies into a baking dish with a handful of other ingredients and watch in amazement as it bakes to creamy perfection!
PREP: Start by measuring out the milk and setting it aside for now. Preheat oven to 400 degrees F. Generously grease a 9x13-inch pan with cooking spray. Drain tuna and set aside.
COMBINE: Add the following ingredients in this order to the pan: uncooked pasta, sprinkle flour evenly on top, add seasonings (thyme, mustard, onion, and garlic powder), and salt/pepper to taste (I add 1 tsp salt and 3/4 tsp pepper), minced garlic, chicken broth/stock, milk, and butter (cut into 2 pieces). Stir well. Cover pan with foil and bake for 20 minutes.
BAKEAGAIN: Remove foil and stir ingredients together really well. Add in frozen peas and carrots. Stir through. Add in 1 cup Cheddar cheese and stir through again. Place tuna on top of ingredients in one even layer. Gently press into the mixture (no need to stir in it). Sprinkle the remaining 1/2 cup Cheddar on top. If adding optional panko topping (Note 5), add it now in one even layer. Return pan to the oven, uncovered, and bake for another 15-20 minutes or until pasta is tender and the top is golden brown (don't over-bake or the sauce will dry out). Remove from oven and let stand for 5 minutes. Enjoy immediately!
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Notes
Note 1: Rotini: This recipe works best with this specific pasta -- it's the best at soaking everything up and bakes through perfectly in the specified time. Other pasta shapes may hide the flour so the dish won't properly thicken. If using other pasta shapes, whisk the flour with 1/4 cup of the chicken broth/stock first before adding to the casserole dish. Ensure whatever pasta is being used has a similar boil time to rotini (9-11 minutes).Note 2: Chicken stock/broth: The better the stock, the more flavor this dish will have. We love and use Swanson's chicken stock. If using chicken broth, you may need a bit more seasoning.Note 3: Whole milk: Remove from the fridge, measure, and set aside before starting to cook. Room-temperature milk will heat quicker! This is intended to be a creamy recipe, and the lower-fat milk choices won't achieve the right texture. That said, you can use 1% or 2% (for a less creamy dish). Unfortunately, skim milk or a dairy milk alternative doesn't work the same in this recipe.Note 4: Frozen veggies: Use 12 ounces of whatever frozen veggie you like best -- all peas, peas and carrots, all corn, or peas and corn.Note 5: Optional topping: Melt 2 tablespoons butter in a large skillet over medium-high heat. Once melted, add in panko and salt to taste, I add a heaping 1/4 teaspoon. Stir constantly until lightly browned then sprinkle over the casserole. (Don't want to use stovetop/pan? Just melt butter in the microwave and mix panko through with heaping 1/4 teaspoon salt.)