A skinny version of potato gratin, using 1% milk and vegetable broth. And some of the potatoes are replaced with slices of a fennel bulb.
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Potato gratins are a classic dish, but are also amenable to adjustments. While I never pass up the more traditional potato gratin, I like to skinny it up with vegetable broth and low-fat milk in place of the heavy cream. And this version swaps out some of the potato slices for fennel.
🧅 Main Ingredients + Notes
The secret to faster and easier meals often lies in the ingredients. For example, store-bought items and ingredients you make ahead and store in the refrigerator (or freezer) can turn a 60-minute recipe into a 30-minutes meal or less.
For the all of the ingredients, measurements and directions, go to the Recipe Card at the bottom of this post.
- Potatoes - I used russet potatoes, but Yukon gold potatoes are totally fine.
- Fennel bulb
- Swiss cheese - I like Gruyere, but any Swiss cheese will work.
- Parmesan cheese
- Leek confit - Leek confit is just a fancy way of saying leek cooked in butter and olive oil until completely soft. You can substitute yellow onions sautéed in olive oil until softened.
- Thyme - either dried or fresh.
- Rosemary - either dried or fresh.
- Unsalted butter
- All-purpose flour
- Low-fat milk
- Vegetable broth - I use Better Than Bouillon - Roasted Vegetable Paste flavor.
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🔪 Recommended Equipment
- Chef's knife
- Medium skillet - for cooking the leeks (or yellow onions)
- Vegetable peeler
- Hand-held mandolin
- Medium pot - for making the roux
- Whisk
- Cheese grater
📝 Instructions Overview
Detailed instructions for making this potato and fennel gratin are in the recipe card below, but here's a quick overview!
Step 1
Make the leek confit. Either make the leek confit, or sauté the diced onions in either olive oil or butter.
Step 2
Prep the potatoes and fennel. Peel the potatoes. Using either a hand-held mandolin or a sharp chef's knife, slice the potatoes and fennel.
Step 3
Combine. Combine the potatoes, fennel, cooked onion, two-thirds of the grated cheeses, thyme, rosemary, salt and pepper in a large bowl. Dump into a baking dish.
Step 4
Make the roux. Melt the butter in a small skillet and whisk in the flour. Once it becomes a paste, cook it for a few minutes, occasionally nudging it around the skillet.
Combine the milk and broth together in a large measuring cup, and gradually whisk into the flour and butter paste. Constantly whisk until you have a smooth liquid. Bring to a simmer for a few minutes until it starts to thicken. Pour over the potatoes and fennel in the baking dish.
Step 5
Bake. Cover the baking dish with foil and bake. About 10 minutes before the gratin is done, remove the foil, add more cheese to the top, and slide back in the oven to finish. Serve hot.
⏰ Tips to Simplify and Save Time
- Grate the cheeses ahead of time.
- Use sautéed onions instead of the leek confit.
💡Ideas for Possible Variations
Top with gremolata breadcrumbs or breadcrumbs dotted with a few pats of butter.
🤷♀️ FAQ
Do I need to make a roux for this potato and fennel gratin?
Yes. Most potato gratins use heavy cream as one of the ingredients, which naturally thickens when heated. Low-fat milk won't do that. So, in order to get a sauce, a roux is necessary which is made with equal parts of butter and all-purpose flour.
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Skinny Potato and Fennel Gratin
Equipment
- box grater
- Aluminum foil
Ingredients
- 2 ½ large russet potatoes
- 2 bulbs fennel
- ¼ cup grated Gruyere cheese
- ¼ cup grated Parmesan cheese
- 1 cup Leek Confit or 2 cups diced yellow onions
- 1 teaspoon dried rosemary or 2 tablespoons fresh rosemary
- 1 teaspoon fresh thyme leaves or 2 tablespoons fresh thyme
- 1 teaspoon kosher salt to taste
- ¾ teaspoon freshly ground pepper to taste
- 2 tablespoons unsalted butter
- 3 tablespoons all-purpose flour
- 2 cups vegetable broth
- ⅓ cup low-fat milk
Instructions
- Preheat the oven to 400 degrees F.
- If using sautéed onions in place of the leek confit, sauté them in 1 tablespoon of olive oil or unsalted butter until softened.
- Thinly slice the potatoes and fennel using either a sharp chef's knife or a small hand-held mandolin. I use the second thinnest setting on my mandolin, creating slices that are an even thickness, and only ⅛" thick. The thicker the slices, the longer it will take for the gratin to cook.
- Combine the potatoes, fennel, leek confit (or cooked onions), two-thirds of the grated cheeses, thyme, rosemary, salt and pepper in a large bowl. Gently toss, and transfer to a baking dish. (The remaining grated cheese will be added to the gratin when it's almost completely cooked.)
- In a small skillet over medium heat, melt the butter. When the butter is melted and sizzling, whisk in the flour, one tablespoon at a time. Cook for a 2 - 3 minutes, occasionally whisking, to cook the flour.
- Combine the vegetable broth and milk together in a measuring cup, and slowly whisk it into the flour/butter mixture starting with about two tablespoons at a time. It will start as a paste, but as you add the broth, it will become a roux sauce. Once a thick sauce is formed, add the broth in a steady, but slow, stream, steadily whisking. Bring to a gentle simmer, and simmer for a few minutes to allow it to thicken, and pour over the potato gratin.
- Cover the gratin with foil, and place the baking dish on a baking sheet. Bake for 45 minutes. Test to make sure the potato slices are tender.Uncover, sprinkle on the last of the cheese and bake for another five to ten minutes uncovered, or until the cheese is melted.
- Serve piping hot.
apuginthekitchen
I love this Susan, potato gratin is one of my favorite guilty pleasure and the addition of the leek confit takes this over the top. You always post such amazing recipes, am making the leek confit today and I will have to use some of it in this gratin.
The Wimpy Vegetarian
Oh I hope you enjoy it!! Thanks so much Suzanne!!
lapadia
Good morning Susan! Enjoy reading your leading stories, packed with information worth knowing. This recipe and your leek confit are wonderful we still have leeks in the garden and I'm always looking for recipes. I'm not on FB anymore and always looked forward to your posts out there so now I look forward to my email recipe notice 🙂 Happy New Year!
The Wimpy Vegetarian
Thanks so much Linda! I did get your message that you've exited FB. The kids and grandchildren were here last weekend, and I've been sick all week. Horribly behind on life. We will definitely continue to visit with each other through our blogs and Food52 🙂 Happy New Year to you too!
lapadia
I hope you are feeling much better by now, hate being sick.
The Wimpy Vegetarian
Ditto, Linda, and thanks. I just hate being sick. Thankfully today is the first day I feel like I'm turning the corner on it.
The Wimpy Vegetarian
Oh, and I'm so sorry about your Seattle Seahawks. I thought they had it. Who know Atlanta would score a field goal in 30 seconds. We in SF wanted Seattle to win too.
Jamie (Mama.Mommy.Mom.)
Wow... just wow! Those look delicious!
The Wimpy Vegetarian
Thanks Jamie!! And thanks for stopping by 🙂
Choc Chip Uru
I'm very partial to gratin so you have made my morning 🙂
Cheers
Choc Chip Uru
The Wimpy Vegetarian
Thanks CCU!! And a very Happy New Year to you!
Cass @foodmyfriend
When I first saw this post I thought 'skinny' gratin?! I love potatoes. They are like my crack 😛 Haha! I rarely go a day without them. This gratin looks awesome. You added my other favourite, fennel! So under rated 🙂 No bacon for me please!
The Wimpy Vegetarian
The bacon adds absolutely nothing in my opinion. So definitely make this without the bacon. It was a bone I threw to my husband :-).
mjskit
Potatoes get such a bad rap! Thanks for supporting them as a good food! Another wonderful dish Susan!!! Having had the confit, I know that his gratin would be delicious and the bacon - oh yea! BTW - I used the leek confit oil to sauteed up some mushrooms tonight and served on top of mashed potatoes. YUM!!! Guess I should have added bacon. 🙂
The Wimpy Vegetarian
MJ, I am just so delighted that you’re enjoying the leek confit. I made some more today and drained the oil off once they cooled to reserve for another use. I loved that idea. Now I’ve got this smooth spread I’m considering for a crostini. Bacon goes well with this confit, but then I think bacon goes well with just about anything 🙂
Lyn @LovelyPantry
I'm glad you posted this, Susan. I am planning on exploring potatoes. I use alot of sweet potatoes, but regular potatoes are not bad at all. This recipe looks so flavourful!!!
Julia {The Roasted Root}
This post is so thorough and informational! I enjoyed reading it and am psyched that you're concentrating on roots this month! People don't cook with them nearly enough and they can be so tasty! Your gratin looks amazing - potato and cheese, don't mind if I do!!
Terra
Wow, I haven't stopped by in awhile, I hope you are well! I love making fennel salads, but I have not added fennel in a warm dish. This recipe sounds delicious, Hugs, Terra
plasterer bristol
Hmm these look delicious, thanks for posting up this recipe, looks quite simple to make.
Simon