Creamy Fennel and Potato Gratin

Here’s my go-to fennel and potato gratin recipe, with layers of thinly sliced potatoes and fennel, plenty of garlic and herbs, all baked in a creamy sauce until golden brown and bubbling.

This gratin has become a regular at our Sunday dinners, and I always make a bigger batch than needed because everyone asks for seconds. And honestly, the leftovers taste even better the next day – if there are any!

What Kind of Fennel Should I Use?

Fresh fennel bulbs are what you’ll want to look for at the grocery store or farmer’s market for this gratin. When shopping, pick fennel bulbs that are clean, white or pale green, and feel heavy for their size – they should be firm and tight, not splitting or flowering at the top. The bulbs should be free from brown spots or blemishes, and the fronds (those feathery green parts on top) should look fresh if they’re still attached. While you can find fennel year-round, it’s at its best and most flavorful during fall and winter months. If you’re new to cooking with fennel, don’t worry about the size too much – both smaller and larger bulbs will work well in a gratin, though larger ones might need an extra minute or two of cooking time.

Options for Substitutions

This cozy gratin recipe can be adapted with several ingredient swaps if needed:

• Fennel: If fennel isn’t your thing or you can’t find it, try using celery (though you’ll get a different flavor profile) or leeks, which offer a mild, sweet taste that works well in gratins.
• Potatoes: Any kind of potato works here – russets, yukon golds, or red potatoes. You could even try sweet potatoes for a different spin, though they’ll cook a bit faster so keep an eye on them.
• Parmesan cheese: No parmesan? Try Pecorino Romano, aged Gruyere, or even a sharp cheddar. For dairy-free folks, nutritional yeast can add a nice cheesy flavor.
• Butter: You can swap butter with olive oil or dairy-free butter alternatives. If using olive oil, use about 45ml instead of 50g of butter.
• Onions: Regular yellow onions can be replaced with shallots (use 6-7), red onions, or even leeks (use 2-3 large ones, white parts only).

Watch Out for These Mistakes While Cooking

The biggest challenge when making fennel and potato gratin is getting the vegetables to cook evenly – slicing your fennel, onions, and potatoes to the same thickness (about 1/8 inch) ensures everything will be perfectly tender at the same time. A common error is undercooking the vegetables before adding the cheese topping, so make sure to test them with a fork for tenderness before adding the final layer of parmesan. To prevent a watery gratin, it’s crucial to let the dish rest for 15-20 minutes after baking, which allows the cream to thicken and settle. For the crispiest top layer, position your baking dish in the upper third of the oven during the final 10 minutes of cooking, and don’t cover the gratin while it’s resting.

What to Serve With Fennel and Potato Gratin?

This rich and creamy gratin works really well as a side dish, but it can also shine as the main star of your meal. When I serve it as a main course, I like to pair it with a simple arugula salad dressed with lemon juice and olive oil – the peppery greens and bright citrus help balance out the richness of the gratin. For a heartier meal, you can add some grilled or roasted chicken on the side, letting the sauce from the gratin create a nice complement to the meat. If you’re keeping things vegetarian, roasted cherry tomatoes or sautéed mushrooms make great partners to this dish, adding nice color and extra flavor to your plate.

Storage Instructions

Keep Fresh: This cozy fennel and potato gratin can hang out in your fridge for up to 3 days when stored in an airtight container. The flavors actually get even better after a day as they have time to mingle together!

Freeze: Good news – you can freeze this gratin for up to 2 months! Just wrap it well in foil and pop it in a freezer-safe container. I like to cut it into portions before freezing, making it super easy to grab just what I need later.

Warm Up: To bring your gratin back to life, cover it with foil and warm it in a 350°F oven for about 20-30 minutes until heated through. If it’s frozen, let it thaw overnight in the fridge first. The foil helps keep the top from getting too brown while reheating.

Make Ahead: You can assemble this gratin up to 24 hours before baking – just cover and keep it in the fridge. When you’re ready to cook, let it sit at room temperature for 30 minutes before popping it in the oven. This makes it perfect for prepping ahead for dinner parties!

Preparation Time	15-20 minutes
Cooking Time	30-40 minutes
Total Time	45-60 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 800-900
• Protein: 20-25 g
• Fat: 50-60 g
• Carbohydrates: 80-90 g

Ingredients

• 50g butter, plus extra for greasing
• 3 large fennel bulbs
• 3 onions
• 600g peeled large potatoes
• 2 crushed garlic cloves
• 50g parmesan cheese, grated (or a vegetarian alternative)

Step 1: Prepare the Oven and Dish

Preheat your oven to 200C/400F/Gas 6, or 180C if you’re using a fan oven.

Butter an ovenproof serving dish to ensure your vegetables won’t stick during baking.

Step 2: Cut the Vegetables

Trim the tops from the fennel bulbs and cut each bulb in half through the root.

Then, cut each half lengthways into three wedges.

Similarly, cut the onions into six wedges.

For the potatoes, slice them into wedges matching the size of the fennel pieces to ensure even cooking.

Step 3: Boil the Vegetables

In a large pan of salted water, boil the fennel and onions for about five minutes.

Then, add the potato wedges to the pan and continue boiling for another five minutes, or until both the potatoes and fennel are just tender.

Once done, drain the vegetables thoroughly.

Step 4: Coat Vegetables with Butter and Garlic

Place 50g/1¾oz of butter and some garlic into the same large pan and set it over low heat until the butter is just melted.

Return the drained potatoes, fennel, and onions to the pan, tossing them gently in the melted garlic butter until they are well coated.

Step 5: Bake the Vegetables

Transfer the butter-coated vegetables into the prepared ovenproof dish.

Sprinkle them generously with Parmesan cheese to add a cheesy touch.

Bake in the preheated oven for 30-40 minutes until the dish is piping hot and the top is golden.

Serve hot and enjoy!