Ina Garten's potato-fennel gratin requires just five main ingredients.Garten's potato-fennel gratin also includes heavy cream and Gruyre cheese. Anneta Konstantinides/Business Insider To make Garten's gratin for four, you'll need:1 pound russet potatoes (2 large ones)1 small fennel bulb yellow onion1 cups Gruyre cheese1 cups plus 1 tablespoon heavy creamThe first step is properly cutting the fennel.Garten's recipe was the first time I'd ever cooked with fennel. Anneta Konstantinides/Business Insider I will admit that the first time I made this dish, I had to watch a Martha Stewart YouTube video on how to cut fennel. But if you're an amateur, there's no need to let this herb intimidate you.Make sure to thinly slice the fennel bulb. Anneta Konstantinides/Business Insider First, cut off the stalks as close to the bulb as possible. Then, cut the bulb in half lengthwise.Remove the cores at the bottom. For Garten's recipe, you'll then thinly slice the bulb halves crosswise which should make about two cups of fennel.Pro tip: Don't throw out your stalks and fronds! Stewart recommends using the fronds in salads and saving the stalk to flavor stockpot dishes.Once that's out of the way, get your onion ready.You'll also want to thinly slice your onion. Anneta Konstantinides/Business Insider You should thinly slice your yellow onion for this dish. Peel your potatoes, then slice them crosswise.Peel your potatoes before thinly slicing them. Anneta Konstantinides/Business Insider Garten recommends thinly slicing them by hand or with a mandoline.You'll also need to grate your Gruyre cheese.Garten's recipe calls for the Gruyre cheese to be grated. Anneta Konstantinides/Business Insider Preparing Garten's gratin takes under 10 minutes, which is great when you're juggling multiple dishes for a holiday feast. And don't forget to butter your baking dish!Make sure to butter your baking dish before building the gratin. Anneta Konstantinides/Business Insider If you're making the gratin for four, Garten recommends using a 9-by-9-by-2-inch baking dish. Once you're done with your prep, saut your fennel and onions together.Saut your fennel and onions for 10 to 15 minutes. Anneta Konstantinides/Business Insider Per Garten's recipe, you'll want to add 1 tablespoon of olive oil and tablespoon of unsalted butter to a pan.Then, saut the fennel and onions on medium-low heat for 10 to 15 minutes, until they're tender. While your stove is working away, add your potatoes to a large bowl with the heavy cream.First, add the potatoes and heavy cream to a large bowl. Anneta Konstantinides/Business Insider You'll use 1 cups of heavy cream for this step. Then, add 1 cup of the Gruyre cheese, as well as salt and pepper.Add your Gruyre cheese, plus salt and pepper. Anneta Konstantinides/Business Insider Garten recommends adding teaspoon of salt and teaspoon of pepper to the mix.I really love pepper, so, as you can see, I may have added a touch more. Next, add your sauted fennel and onions on top.Don't forget to add your sauted fennel and onions. Anneta Konstantinides/Business Insider It's almost time to bake!To build the gratin, start by pouring your potato mixture into the baking dish.Smooth your potato mixture in the baking dish. Anneta Konstantinides/Business Insider Gently press down to smooth the potatoes out. Then, mix the rest of your heavy cream and cheese together and sprinkle on top.Then, add the rest of your cheese and heavy cream on top. Anneta Konstantinides/Business Insider Remember, you'll want to use 1 tablespoon of cream and cup of Gruyre for this quick step. After an hour in the oven at 350 degrees Fahrenheit, your gratin will be beautifully browned and bubbly and almost ready to eat.Garten's gratin looks beautifully golden-brown when it comes out of the oven. Anneta Konstantinides/Business Insider Garten recommends letting the gratin sit for 10 minutes before serving it hot.She also notes that the gratin can be cooked a day ahead and reheated at 350 degrees for 30 minutes, a helpful tip if you want to save some time during the holidays. Garten's potato-fennel gratin doesn't just look delicious it tastes incredible, too.And it tastes like a creamy, cheesy dream. Anneta Konstantinides/Business Insider Few things in this world are more comforting than potatoes mixed with heavy cream and cheese. Garten's gratin is creamy and satisfying, thanks to the Gruyre, and the potatoes are perfectly cooked. Since the fennel is sauted, its flavor is mild and sweet rather than overpowering.But one of the best things about the gratin is how well it goes with everything, making it a great sidekick for any meat or holiday side dish. I think the potato-fennel gratin is a perfect side for any holiday spread.I can't wait to make Garten's gratin for Christmas again. Anneta Konstantinides/Business Insider It's so simple to make that you could easily delegate the task to a young budding chef in your family or at least let the kids help you with it in the kitchen. Plus, the gratin is easy to make ahead and reheat before dinner, giving you some much-needed space in the oven for a big holiday menu.And you can't go wrong with creamy potatoes and cheese, especially during the winter season.Believe me, you'll all be fighting for seconds.