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A white baking dish of tuna casserole with a golden cheddar and parmesan crust, one corner scooped out to show tender cauliflower florets, flaked tuna, mushrooms and celery in a creamy cheese sauce.

Keto Tuna Casserole

Classic tuna casserole made low carb with cauliflower florets in place of noodles, a creamy cheddar and cream cheese sauce, and a crisp parmesan top. 30 g protein and about 9 g net carbs per serving.
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Prep Time 20 minutes
Cook Time 25 minutes
Total Time 45 minutes
Servings 6 servings
Calories 446 kcal

Ingredients
  

  • 1 1/2 lb cauliflower florets (1 medium head), cut into 1-inch pieces
  • 4 cans (5 oz each) chunk light tuna in water, drained well
  • 2 tbsp butter, plus more for the dish
  • 1/4 cup diced yellow onion
  • 2 celery stalks, diced
  • 8 oz white mushrooms, sliced
  • 2 cloves garlic, minced
  • 1/2 cup low-sodium chicken broth
  • 4 oz full-fat cream cheese, softened and cubed
  • 1/2 cup heavy cream
  • 1 1/2 cups shredded sharp cheddar, divided
  • 1 tsp yellow mustard
  • 1/2 tsp dried thyme
  • 1/2 tsp salt, or to taste
  • 1/4 tsp black pepper
  • 1/2 cup grated parmesan
  • 2 tbsp almond flour
  • Chopped fresh parsley, for serving

Instructions
 

  • Heat the oven to 400°F (200°C). Butter a 9x13-inch (or 3-quart) baking dish.
  • Steam the cauliflower florets for 5 to 6 minutes, until a knife just slides in. Drain well and let them steam dry in the colander for a few minutes.
  • Melt the butter in a large skillet over medium heat. Add the onion, celery and mushrooms and cook for 7 to 8 minutes, until the mushrooms brown and their liquid cooks off. Add the garlic and cook for 30 seconds.
  • Pour in the chicken broth, then add the cream cheese and heavy cream. Whisk until smooth and simmer gently for 3 to 4 minutes, until the sauce coats a spoon.
  • Take the skillet off the heat. Stir in 1 cup of the cheddar, the yellow mustard, thyme, salt and pepper until the cheese melts.
  • Fold in the drained cauliflower and the drained tuna, breaking the tuna into chunks. Spread it in the baking dish.
  • Sprinkle the remaining 1/2 cup cheddar over the top. Mix the parmesan and almond flour and scatter it over the cheese.
  • Bake for 20 to 25 minutes, until the edges bubble, the top is golden and the center reaches 165°F (74°C) on a thermometer.
  • Let it rest for 5 minutes, then top with parsley and serve.

Notes

Nutrition per serving (1/6 of the casserole): 446 calories, 30 g protein, 12 g total carbohydrates, 3 g fiber, about 9 g net carbs (total carbs minus fiber), 32 g fat. Calculated from USDA FoodData Central. Peas are not included; if you add them, the carbs go up. Drain the tuna and cauliflower well so the casserole isn't watery. Make ahead: assemble, cover and refrigerate up to 1 day, then bake from cold for 10 to 15 minutes longer. Refrigerate leftovers within 2 hours and use within 3 to 4 days. Freeze portions up to 2 to 3 months for best quality, thaw overnight in the fridge, and reheat to 165°F.