You don’t need another bland “healthy” recipe—you need a slam-dunk that tastes like comfort food and still crushes your macros. This Keto Spinach & Mushroom Casserole is rich, cheesy, and ridiculously satisfying without the carb crash. It’s the kind of dish that makes everyone at the table think you cheated, then ask for seconds.
Minimal prep, max flavor, and it reheats like a dream. Want a weeknight winner that doesn’t blow your plan? This is it.
What Makes This Recipe Awesome
- Big flavor, simple method: Sautéed mushrooms, garlicky spinach, and a creamy, cheesy base that bakes into a golden, bubbling top.
No culinary degree required.
- Ultra low-carb: Packed with fiber-rich spinach and umami mushrooms, anchored by fats and protein for stable energy. No sneaky starches, no regrets.
- Meal-prep friendly: Assemble ahead, bake later, or cook once and enjoy leftovers that taste even better the next day.
- Flexible AF (within macros): Add protein, swap cheeses, or scale to feed a crowd. You’re the boss here.
- Comfort-food texture: Creamy interior with a slightly crisp, cheesy top—basically your favorite casserole, minus the carb brick.
Ingredients Breakdown
- Avocado oil or olive oil (2 tbsp): For sautéing; adds healthy fats and flavor.
- Unsalted butter (1 tbsp): Enriches the sauté and deepens the mushroom flavor.
- Cremini or baby bella mushrooms (16 oz), sliced: Meaty, savory base; hold their texture well.
- Fresh spinach (10 oz), roughly chopped: Wilts down into a nutrient-dense green layer.
Frozen works in a pinch (thaw and squeeze dry).
- Garlic (3–4 cloves), minced: Aromatic, essential. Don’t skip unless you’re meeting vampires.
- Cream cheese (6 oz), softened: Creates a rich, cohesive sauce.
- Heavy cream (3/4 cup): Smooths the sauce and carries flavor. For lighter, use half cream/half unsweetened almond milk.
- Grated Parmesan (1/2 cup): Salty, nutty depth; thickens the sauce.
- Shredded mozzarella (1 1/2 cups), divided: Melty, stretchy top layer and body.
- Eggs (2), lightly beaten: Binds the casserole so it sets without flour or starches.
- Ground nutmeg (a pinch): Classic with cream and spinach; subtle, elegant warmth.
- Red pepper flakes (optional, 1/4 tsp): Gentle heat for balance.
- Kosher salt and black pepper: Season to taste at multiple steps.
- Fresh parsley or chives (2 tbsp), chopped: Fresh finish and color pop.
Instructions
- Preheat and prep: Heat the oven to 375°F (190°C).
Grease a 9×9-inch baking dish or similar casserole pan.
- Sauté the mushrooms: In a large skillet, warm the oil and butter over medium-high. Add mushrooms and a pinch of salt. Cook 7–9 minutes, stirring occasionally, until they release moisture and begin to brown.
- Add aromatics: Stir in the garlic and red pepper flakes (if using).
Cook 30–60 seconds until fragrant—don’t burn the garlic unless bitter is your love language.
- Wilt the spinach: Add spinach in batches with a pinch of salt. Cook 2–3 minutes until fully wilted and moisture mostly evaporates. If using frozen spinach, ensure it’s squeezed very dry before warming through.
- Make it creamy: Reduce heat to medium-low.
Add cream cheese and heavy cream. Stir until smooth and silky. Mix in Parmesan, 1/2 cup mozzarella, nutmeg, and black pepper.
Taste and adjust salt.
- Bind it: Remove the skillet from heat. Let the mixture cool 2–3 minutes, then stir in the beaten eggs quickly so they incorporate without scrambling.
- Assemble: Transfer the mixture to the greased dish. Top with the remaining mozzarella, spreading to the edges for maximum cheese coverage.
- Bake: Bake 18–22 minutes until set around the edges and bubbling.
For a golden top, broil 1–2 minutes at the end. Watch closely—golden, not charcoal.
- Rest and garnish: Let it rest 5–8 minutes to firm up. Sprinkle with parsley or chives.
Slice and serve hot.
Preservation Guide
- Fridge: Store in an airtight container for up to 4 days. Reheat covered at 325°F (165°C) for 10–15 minutes or microwave in 45-second bursts.
- Freezer: Cool completely, portion, and wrap tightly. Freeze up to 2 months.
Thaw overnight in the fridge before reheating.
- Make-ahead: Assemble up to 24 hours in advance, cover, and refrigerate. Add 5–8 minutes to bake time if going straight from cold.
- Meal prep tip: Bake in individual ramekins for grab-and-go portions that reheat evenly.
Health Benefits
- Keto-aligned macros: High in fats and moderate protein helps keep you satiated and supports ketosis.
- Micronutrient dense: Spinach is loaded with vitamin K, folate, and magnesium; mushrooms bring B vitamins, selenium, and ergothioneine (an antioxidant MVP).
- Stable energy: The fat-forward profile yields lasting energy without the post-pasta nap. Your afternoon productivity will thank you.
- Blood sugar friendly: Minimal carbs and no refined grains help keep glucose spikes in check, IMO ideal for low-carb lifestyles.
Pitfalls to Watch Out For
- Watery casserole: Don’t rush the sauté.
Cook off mushroom and spinach moisture thoroughly, and squeeze frozen spinach dry like it owes you money.
- Egg scramble vibes: Let the filling cool a couple minutes before mixing in eggs, and stir fast. We’re binding, not making breakfast.
- Bland outcome: Season at every step. Mushrooms and spinach soak up salt—taste, adjust, repeat.
- Greasy top: Use measured cheese amounts and avoid ultra-oily blends.
Grate your own if possible for better melt and less oil separation.
- Rubbery texture: Don’t overbake. Pull when edges are set and center jiggles slightly; it firms as it rests.
Alternatives
- Protein boost: Add cooked Italian sausage, rotisserie chicken, or bacon crumbles (about 1–2 cups). Adjust salt accordingly.
- Dairy tweaks: Swap mozzarella with Gruyère or provolone for deeper flavor; use mascarpone instead of cream cheese for extra silk.
- Veg swap: Kale (finely chopped), Swiss chard, or broccoli riced and pre-sautéed all work.
Keep water content in check.
- Herb upgrade: Fresh thyme or rosemary (go light) complements mushrooms beautifully.
- Spice path: Smoked paprika or a pinch of cayenne for a subtle kick. FYI, a little goes a long way.
- No eggs: Use 1/4 tsp xanthan gum whisked into the cream to thicken, or bake slightly longer until set.
FAQ
Can I make this casserole vegetarian and still high-protein?
Yes. Add ricotta (1 cup) and swap part of the mozzarella for higher-protein cheeses like Gruyère.
You can also mix in diced, sautéed tempeh or crumbled tofu that’s been pressed and pan-seared for texture.
How can I lower the calories without losing the creamy factor?
Use half heavy cream and half unsweetened almond milk, and reduce cheese by 1/4 cup. Keep the cream cheese for texture, or replace half of it with full-fat Greek yogurt stirred in after baking to avoid curdling.
Is frozen spinach okay?
Absolutely. Thaw completely and squeeze it aggressively in a clean towel to remove excess liquid.
Measure about 10 ounces after draining for best results.
What size pan should I use if I double the recipe?
A 9×13-inch pan works well for a double batch. Add 5–10 minutes to the bake time and check the center for doneness before pulling.
Can I make it spicy?
Yes—add 1/2 teaspoon red pepper flakes to the sauté and finish with a drizzle of chili oil before serving. You’ll get warmth without overpowering the creamy base.
What should I serve with it?
A crisp arugula salad with lemon vinaigrette, roasted asparagus, or a simple cucumber salad.
If you want more protein, serve alongside grilled chicken thighs or steak tips.
How do I prevent the top from over-browning?
Tent loosely with foil once the cheese is golden, or move the dish to a lower oven rack. If broiling, stay close—30 seconds is the difference between “perfect” and “oops.”
Wrapping Up
This Keto Spinach & Mushroom Casserole hits the sweet spot: comfort-food flavors, clean ingredients, and a set-it-and-forget-it cook time. It’s weeknight-easy, dinner-party good, and meal-prep approved.
Make it once, tweak it to your taste, and you’ve got a reliable, guilt-free staple in your rotation. Your macros will behave, your taste buds will celebrate, and your leftovers won’t last long—consider that your only “problem.”
