I first made this casserole on a rainy weeknight when I wanted something cozy, low-carb, and fast. The result was a creamy, garlicky chicken topped with golden melted cheese and deeply browned mushrooms — a meal that feels indulgent but stays keto-friendly. It’s the kind of dish you can serve to family, pack for lunches, or make for a dinner party with very little fuss. If you enjoy rich one-pan chicken dinners like the lemon garlic butter chicken thighs, this recipe will fit right into your weeknight rotation.

Why you’ll love this dish

This casserole gives you big flavor with minimal carbs and little cleanup. It’s perfect for:

Quick weeknight dinners — about 40 minutes from start to table.
Keto and low-carb meal plans — heavy cream and cheese keep the sauce rich without starchy thickeners.
Family-friendly comfort food — mild, cheesy flavors that appeal to kids and adults.
Make-ahead reheating — leftovers reheat well for easy lunches.

“Comforting, creamy, and so simple — the mushrooms add an umami hit that makes this feel special.” — a home-cooked favorite

Beyond taste, this recipe is forgiving: you can swap cheeses, change herbs, and still get a satisfying result. If you want another hands-off chicken option for busy nights, try the slow-cooker style honey garlic chicken for variety.

How this recipe comes together

Think of the casserole in three clear stages:

Sauté mushrooms and garlic until the mushroom moisture evaporates — this concentrates flavor and prevents a soggy sauce.
Season and arrange chicken in a shallow dish, then spoon the mushroom-garlic mixture on top.
Make a creamy, cheesy sauce, pour over the chicken, top with more cheese, and bake until the chicken hits 165°F (74°C).

This overview helps you move through the steps without surprises: brown first, assemble second, bake last. If you like casseroles with caramelized onions and similar textures, you’ll appreciate the technique used in this French onion chicken casserole.

What you’ll need

2 boneless, skinless chicken breasts (about 1 to 1.25 lb total) — trim and optionally pound to even thickness for uniform cooking.
8 oz mushrooms, sliced (cremini or button) — cremini gives more depth.
3–4 garlic cloves, minced — adjust for your taste.
1 cup heavy cream — full-fat keeps the sauce rich and keto-friendly.
1 to 1 1/2 cups shredded cheese (mozzarella or cheddar) — cheddar for sharpness, mozzarella for melt.
1–2 tbsp olive oil or butter — butter adds richness.
Salt and freshly ground black pepper, to taste.
Fresh or dried herbs (thyme or parsley; 1–2 tsp dried or 1 tbsp fresh).

Notes and substitutions:

For a lighter dairy option, use half-and-half but expect a thinner sauce.
Add a splash of chicken broth if you prefer a less rich sauce.
For an extra umami boost, finish mushrooms with a small splash of dry white wine while sautéing.

Step-by-step instructions

Preheat the oven to 375°F (190°C).
Warm 1–2 tablespoons olive oil or butter in a skillet over medium heat.
Add sliced mushrooms and the minced garlic. Sauté, stirring occasionally, until mushrooms are deeply browned and any released liquid has evaporated, about 6–8 minutes. Season with salt and pepper. Browning is key — don’t rush this step.
Season both sides of the chicken breasts with salt and pepper and place them in a shallow baking dish. If breasts are thick, you can butterfly or lightly pound them for even cooking.
Spoon the sautéed mushroom and garlic mixture evenly over the chicken.
In a bowl, whisk the heavy cream with your chosen herbs. Stir in most of the shredded cheese, reserving a handful for the top. Pour this creamy mixture over the chicken and mushrooms.
Sprinkle the remaining cheese over the casserole to form a golden crust.
Bake for 25–30 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and the sauce is bubbly. If your chicken was on the thin side, check earlier to avoid drying.
Let the dish rest for 5 minutes before serving to allow the sauce to settle.

Best ways to enjoy it

Serve over cauliflower rice or alongside steamed broccoli for a low-carb plate.
Spoon onto a bed of sautéed spinach or zucchini noodles for extra greens.
For a heartier meal, pair with roasted asparagus and a simple mixed-green salad.
Garnish with chopped fresh parsley or thyme and a grind of black pepper for contrast.

Plating tip: spoon a little of the bubbly cream onto the plate first, place the chicken on top, and finish with fresh herbs for a rustic, restaurant-style presentation.

Storage and reheating tips

Refrigerator: Store cooled leftovers in an airtight container for up to 3–4 days.
Reheating: Warm gently in a 325°F oven for 10–15 minutes or microwave in 30-second bursts until heated through. Add a splash of cream if the sauce tightens.
Freezing: Freeze portions in freezer-safe containers for up to 2 months. Thaw overnight in the fridge before reheating.
Food safety: Always cool dishes before refrigerating and reheat to at least 165°F (74°C) before serving.

Helpful cooking tips

Dry mushrooms well: Pat mushrooms with paper towels before cooking to help them brown instead of steam.
Even chicken thickness: Pound thicker breasts to ¾–1 inch for even bake time.
Cheese timing: Stir most cheese into the sauce so it melts uniformly; reserve some for that golden top.
Avoid watery sauce: Evaporating mushroom liquid fully and using enough cheese helps thicken the sauce without flour.
Use a probe thermometer: It’s the most reliable way to ensure juicy, safe chicken.

Creative twists

Add bacon: Crisp and crumble 3–4 strips into the mushroom mixture for smoky flavor.
Spinach and artichoke version: Fold in 1 cup chopped cooked spinach and a few chopped artichoke hearts for a creamy dip-inspired casserole.
Dairy-free: Swap heavy cream for coconut cream and use a dairy-free cheese for a low-carb but dairy-free option (note flavor will change).
Sun-dried tomatoes and basil: Stir in chopped sun-dried tomatoes and fresh basil for a Mediterranean spin.
Make it a skillet meal: Sear thin-cut chicken, add mushrooms and cream, then finish under the broiler for a quicker one-pan approach similar to the technique used in many casserole variations like this French onion chicken casserole.

Common questions

Q: Can I use chicken thighs instead of breasts?
A: Yes. Boneless, skinless thighs are more forgiving and stay juicier. Reduce baking time slightly if using smaller pieces and check for 165°F (74°C).

Q: Is this recipe truly keto?
A: Yes — the recipe uses heavy cream and cheese instead of flour or starches, keeping carbs low. Check labels on cheeses or add-ins for any hidden carbs.

Q: My mushrooms released too much liquid — how do I fix a thin sauce?
A: Cook mushrooms longer to evaporate excess liquid before assembling. If the sauce is already thin, simmer it on the stovetop briefly with a bit more cheese to thicken, or add a small slurry of xanthan gum (very little — start with 1/8 tsp).

Q: Can I assemble ahead and bake later?
A: You can assemble the casserole up to 24 hours ahead and refrigerate. Bake from chilled, adding a few extra minutes until the internal temperature reaches 165°F (74°C).

Q: How can I make this low-sodium?
A: Use low-sodium broth if adding broth, reduce added salt, and choose lower-sodium cheeses.

Conclusion

This Keto Garlic Mushroom Chicken Casserole is an easy, comforting weeknight winner — rich, savory, and reliably low-carb. If you want more inspiration for creamy keto chicken casseroles, see Keto Chicken Mushroom Casserole – Creamy Low Carb Goodness! for a slightly different take, or try the one-pan version at Keto Chicken Mushroom Casserole (One Pan) – Sugar-Free Mom for another simple method.