Make this tuna broccoli alfredo casserole for dinner tonight - it's easy to assemble and low carb. Tuna and fresh chopped broccoli are coated in a homemade alfredo sauce and topped with shredded mozzarella cheese.
If you're looking for a new low-carb dinner idea, try out my recipe for tuna broccoli alfredo casserole. It's filled with protein-packed albacore tuna and fresh chopped broccoli.
The best part? The creamy homemade alfredo sauce. Don't be intimidated by making this sauce from scratch - it's surprisingly simple! Made with heavy cream, butter, and fresh grated parmesan cheese, this sauce is flavorful, rich, and comforting!
Make this tuna broccoli alfredo casserole for a quick weeknight meal. You'll have this casserole in the oven with only 10 minutes of prep.
Ingredients and substitutions
Tuna - I recommend using chunk white albacore tuna in water. You'll need three 5 ounce cans, which equals 4 ounces each in drained tuna. You should see both measurements on the cans.
Broccoli - I recommend using fresh, raw broccoli for this recipe. Frozen or thawed broccoli will add extra moisture to your casserole, which I do not recommend (see my section below on watery casserole).
Butter - Salted or unsalted butter works in this recipe. You may want to reduce the listed salt by ⅛ teaspoon if you're using salted butter and are sensitive to salt in recipes.
Heavy cream - Necessary to make your alfredo sauce thick and rich. I do not recommend substituting with any other dairy. Thinner dairy like milk or half & half will result in a thin sauce.
Mozzarella - Fresh shredded mozzarella works best in this recipe. I do not recommend using pre-shredded cheese for this recipe. Pre-shredded cheeses are coated in powders to prevent clumping. When melted, this powder will cause your sauce to be grainy.
Parmesan cheese - I recommend grating your cheese fresh from a block for best flavor and smooth melted texture (just like the mozzarella cheese).
Seasoning - Salt, pepper, Italian seasoning, and fresh garlic add mild, savory flavor to the dish. I don't recommend omitting any of these ingredients. Fresh garlic could be substituted with ½ teaspoon of garlic powder if needed.
Tips and tricks
Do not make any ingredient substitutions - Heavy cream is necessary to make a creamy, rich, and thick sauce. Substituting with half & half or milk will result in a thin sauce.
Pat broccoli dry after rinsing - It should go without saying, but adding wet broccoli to your casserole will make it watery. Pat your broccoli dry after rinsing or use a salad spinner to remove excess moisture.
Don't use frozen broccoli - I do not recommend using frozen broccoli for the same reason. It contains excess moisture that will make your casserole watery once baked. This casserole doesn't bake long enough to thaw and cook broccoli, so your broccoli will likely still be a bit raw if frozen broccoli is added.
Drain tuna well - Drain your canned tuna very well. Just like with the broccoli, adding extra moisture from your canned tuna will make your casserole watery.
Thin sauce? Allow your casserole to set at room temperature for 5-10 minutes before serving. As your casserole sets, the sauce will continue to thicken.
Storage
Unfortunately, alfredo sauce does not do well as a leftover. Cream based sauces do not freeze well and alfredo sauce in particular does not reheat well.
Why does this happen? In short, the emulsion breaks. An emulsion is formed between the liquids and the fats during the cooking process, which breaks when reheated in a microwave or on the stove top.
This leaves you with a separated sauce. One part is gloppy/cheesy and the other part is pure butter. Not very appetizing!
You can keep leftover casserole to reheat the next day, but keep in mind that your sauce will likely separate during the reheating process.
Frequently asked questions
Your casserole can turn out watery for several reasons:
- Broccoli was added while still frozen or wet.
- Heavy cream was substituted with a thinner dairy product.
- Tuna wasn't drained.
- Sauce wasn't cooked long enough on the stovetop. Times included in the recipe card are estimates and I'd recommend relying more on visual cues instead.
If your casserole turns out watery, allow it to set for up to ten minutes. The sauce will thicken slightly during this time.
I recommend using chunk white albacore tuna in water for this recipe, but any type of canned tuna (or canned chicken) will work. White tuna has a firmer texture and milder flavor than light tuna varieties. I like using white tuna because it blends well with the other flavors of the casserole. It also retains its shape for the most part when stirred into the sauce. Light tuna is usually darker in color and made with several species of tuna. It also has a flakier texture and a stronger tuna flavor. However, light tuna is also generally less expensive than white tuna.
Recommended
📖 Recipe
Tuna Broccoli Alfredo Casserole
Ingredients
- ¼ cup unsalted butter
- 2 cloves garlic, minced
- 1 cup heavy cream
- ½ teaspoon Italian seasoning
- ½ teaspoon salt
- ¼ teaspoon pepper
- 1 cup freshly grated parmesan cheese
- 15 ounces canned white chunk albacore tuna in water, drained
- 4 cups chopped broccoli florets
- 1 cup shredded mozzarella cheese
Instructions
- Preheat oven to 350℉. Lightly grease an 8x8 square baking dish (or other 2 quart dish) and set aside.
- In a sauté pan over medium heat, add butter. Once melted and bubbling, add minced garlic and cook for 1 minute. Add heavy cream, Italian seasoning, salt, and pepper. Stir and cook for about 2-3 minutes, or until sauce has thickened.
- Add parmesan cheese and stir until melted. Remove from heat and stir in drained tuna and broccoli florets. Pour into prepared baking dish and spread into an even layer. Top with shredded mozzarella cheese.
- Bake, uncovered, for 25 minutes, or until hot and bubbling throughout. Remove from oven and allow to set for 5 minutes before serving.
Equipment Recommendations
Notes
- To prevent a watery casserole: Drain your canned tuna very well. If rinsing your broccoli, pat dry before adding to casserole.
- Fresh-grated cheese is best: Use freshly grated parmesan cheese for best results. Pre-shredded cheeses are coated in anti-clumping powders. When melted, these powders will make your sauce grainy.
- Leftovers: Alfredo sauce will separate if reheated - this dish does not do well as a leftover.
- Tuna measurements: 15 ounces of canned tuna = 12 ounces of canned tuna after draining
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