This Keto Zucchini Gratin is the cozy, bubbling side dish I make when I want something that feels special but stays low carb. Thin-sliced zucchini bakes in a garlicky parmesan-gruyere cream until golden and irresistible. It is weeknight simple and dinner-party worthy all at once.
Keto Zucchini Gratin Recipe (Creamy, Cheesy & Easy)
Equipment
- 1 Mandoline or sharp knife
- 1 Sheet pan
- 1 Paper towels
- 1 Medium saucepan
- 1 Whisk
- 1 2-quart gratin dish or 9×9 inch baking dish
- 1 Rimmed baking sheet to catch drips
- 1 Oven broiler (optional) for browning
Ingredients
Zucchini Gratin
- 2 lb zucchini thinly sliced 1/8 inch
- 1 tsp kosher salt for draining the zucchini
- 1 tbsp butter
- 1 tbsp olive oil
- 3 cloves garlic minced
- 1 cup heavy cream
- 2 oz cream cheese cubed
- 1 tsp Dijon mustard
- 0.5 tsp dried thyme or 1 tsp fresh thyme leaves
- 1 pinch ground nutmeg
- 0.25 tsp red pepper flakes optional
- 1.5 cups gruyere shredded, divided
- 0.5 cup parmesan finely grated, divided
- 1 large egg yolk optional but recommended
- Freshly ground black pepper to taste
- 2 tbsp parsley chopped, for garnish
Instructions
- Slice zucchini 1/8 inch thick using a mandoline or sharp knife. Spread on a sheet pan, sprinkle with 1 tsp kosher salt, and let stand 20 to 30 minutes to draw out water. Pat very dry with paper towels.
- In a medium saucepan over medium heat, warm butter and olive oil. Add garlic and cook 30 to 60 seconds until fragrant. Pour in heavy cream, add cream cheese, Dijon, thyme, nutmeg, and red pepper flakes. Simmer 2 to 3 minutes, whisking until smooth and slightly thickened. Off heat, whisk in 1 cup gruyere and 1/4 cup parmesan until melted. Whisk the egg yolk in a small bowl, then slowly stream in 2 tablespoons of the hot sauce to temper. Return the tempered yolk to the pan and whisk until glossy. Season with black pepper to taste.
- Heat oven to 400 b0F (200 b0C). Grease a 2-quart gratin dish or 9 x 9 inch baking dish. Place the dish on a rimmed sheet pan to catch any bubbling.
- Shingle a layer of zucchini into the dish. Spoon over a third of the sauce. Repeat 2 more times to use all zucchini and sauce. Top with remaining 1/2 cup gruyere and 1/4 cup parmesan.
- Bake 20 to 25 minutes until the edges are bubbling and the top is lightly browned. For extra color, broil 1 to 2 minutes, watching closely.
- Let the gratin rest 10 minutes so it sets cleanly for scooping. Sprinkle with parsley and serve hot.
Notes
Nutrition
Why You’ll Love This Keto Zucchini Gratin
- Ultra creamy and cheesy with perfectly tender zucchini.
- Truly low carb and keto friendly without missing the comfort-food factor.
- Simple prep using everyday ingredients and one pan for the sauce.
- Make ahead friendly and great for both weeknights and holidays.
- Customizable with your favorite cheeses and herbs.
Keto Zucchini Gratin Ingredients & Substitutions
- 2 lb zucchini, thinly sliced 1/8 inch (about 900 g). Swap: yellow squash or a mix of both.
- 1 tsp kosher salt for draining the zucchini.
- 1 tbsp butter + 1 tbsp olive oil. Swap: all butter or ghee for a richer flavor.
- 3 cloves garlic, minced. Swap: 1 tsp garlic powder in a pinch.
- 1 cup heavy cream (240 ml). Swap: 3/4 cup heavy cream + 1/4 cup unsweetened almond milk; or full-fat coconut cream for dairy-light variation.
- 2 oz cream cheese, cubed (56 g) to thicken without flour. Swap: mascarpone.
- 1 tsp Dijon mustard for brightness.
- 1/2 tsp dried thyme or 1 tsp fresh thyme leaves. Swap: Italian seasoning or fresh rosemary, finely chopped.
- Pinch ground nutmeg for classic gratin depth.
- 1/4 tsp red pepper flakes, optional.
- 1 1/2 cups shredded gruyere (about 6 oz), divided. Swap: fontina, cheddar, or provolone.
- 1/2 cup finely grated parmesan (about 40 g), divided. Swap: pecorino romano.
- 1 large egg yolk to enrich and stabilize the sauce. Optional but recommended.
- Freshly ground black pepper.
- 2 tbsp chopped parsley for garnish.
Note: If you like the sauce even thicker, whisk in a tiny pinch of xanthan gum at the end. A little goes a long way.
Step-by-Step Instructions to Make Keto Zucchini Gratin
1. Prep and drain the zucchini
Slice zucchini 1/8 inch thick using a mandoline or sharp knife. Spread on a sheet pan, sprinkle with 1 tsp kosher salt, and let stand 20 to 30 minutes to draw out water. Pat very dry with paper towels. This keeps the gratin from turning watery.
2. Make the keto cream sauce
In a medium saucepan over medium heat, warm butter and olive oil. Add garlic and cook 30 to 60 seconds until fragrant. Pour in heavy cream, add cream cheese, Dijon, thyme, nutmeg, and red pepper flakes. Simmer 2 to 3 minutes, whisking until smooth and slightly thickened. Off heat, whisk in 1 cup gruyere and 1/4 cup parmesan until melted. Whisk the egg yolk in a small bowl, then slowly stream in 2 tablespoons of the hot sauce to temper. Return the tempered yolk to the pan and whisk until glossy. Season with black pepper to taste.
3. Preheat and prepare the dish
Heat oven to 400°F (200°C). Grease a 2-quart gratin dish or 9 x 9 inch baking dish. Place the dish on a rimmed sheet pan to catch any bubbling.
4. Layer the gratin
Shingle a layer of zucchini into the dish. Spoon over a third of the sauce. Repeat 2 more times to use all zucchini and sauce. Top with remaining 1/2 cup gruyere and 1/4 cup parmesan.
5. Bake until bubbly and golden
Bake 20 to 25 minutes until the edges are bubbling and the top is lightly browned. For extra color, broil 1 to 2 minutes, watching closely.
6. Rest and serve
Let the gratin rest 10 minutes so it sets cleanly for scooping. Sprinkle with parsley and serve hot.
Tips for Success
- Salt and dry the zucchini. This single step keeps the texture creamy instead of soupy.
- Shred your own cheese. Pre-shredded blends contain starches that can dull melting.
- Do not boil the sauce after adding the egg yolk. Gentle heat keeps it silky.
- Balance the sauce. Zucchini releases some moisture in the oven, so the sauce should start a bit thicker than you think.
- Let it rest. Ten minutes after baking gives you neat, scoopable layers.
Variations of Keto Zucchini Gratin
- Bacon and onion: Sauté 4 slices chopped bacon and 1/2 diced onion; fold into the sauce.
- Herb garden: Add chopped basil and chives with the parsley, plus lemon zest for lift.
- Spicy jalapeño: Stir in 1 finely minced jalapeño with the garlic.
- Mushroom medley: Sauté 8 oz sliced mushrooms, cook off moisture, and layer with zucchini.
- Main-dish upgrade: Add 2 cups cooked shredded chicken and increase sauce by 25 percent.
- Pesto swirl: Dollop 2 tbsp pesto between layers for an herby twist.
Serving Suggestions: What to Pair with Keto Zucchini Gratin
- Protein: Roast chicken thighs, seared steak, grilled salmon, or garlic shrimp.
- Fresh side: Simple arugula salad with lemon vinaigrette or roasted tomatoes.
- Sauces: Chimichurri, lemon butter, or a squeeze of fresh lemon over everything.
- Wine: Chardonnay or pinot noir. Non-alcoholic: Sparkling water with lemon and thyme.
Storage & Reheating Instructions
- Refrigerate: Cool, cover, and store up to 3 to 4 days.
- Reheat: 350°F (175°C), covered, 12 to 15 minutes, then uncover 3 minutes to re-crisp the top. Microwave in short bursts for single portions.
- Freeze: Not ideal due to zucchini’s moisture, but possible. Wrap tightly and freeze up to 2 months. Thaw overnight and reheat as above.
- Leftover ideas: Spoon into an omelet, tuck into lettuce cups, or serve alongside a burger patty.
Memories Made Around the Table
This recipe was my low-carb love letter to my grandmother’s creamy scalloped potatoes. The same cozy flavors, but light enough to enjoy on a Tuesday night.
FAQs
Can I skip the egg yolk?
Yes. The yolk enriches and helps the sauce set, but you can omit it. Simmer the sauce a minute longer or add a tiny pinch of xanthan gum if you want it thicker.
How do I keep the gratin from getting watery?
Salt and drain the zucchini, pat it very dry, and avoid over-saucing. Bake until bubbling and let it rest 10 minutes to set.
Can I use yellow squash instead of zucchini?
Absolutely. Yellow squash works beautifully or use a mix for color.
What are the carbs per serving?
Approximate per serving (1/6 of recipe): 230 to 260 calories, 5 to 6 g net carbs, 18 to 20 g fat, 10 to 12 g protein. Values vary by brands and cheese choices.
Can I make it ahead?
Assemble up to 1 day ahead, cover, and refrigerate. Bake straight from the fridge at 400°F, adding 5 minutes, then broil to brown if needed.
Final Thoughts
This Keto Zucchini Gratin is proof that comfort food can be low carb and deeply satisfying. Keep it in your back pocket for holidays, potlucks, or any night you want a cozy, golden side that steals the show.