My Mum's Leek Gratin | A Family Tradition

This is a family recipe. It's something that my mum makes every year for Christmas, and it's always the first dish on the table to get finished. What I love about this recipe is it can be made ahead of time. It comes together quickly and easily, and it's a crowd-pleaser. Everyone always wants more. So let's get into it. The recipe naturally starts with leeks. First, I peel off the outer layer that always looks dry. I like to think of it as the leeks' own self-grown, biodegradable packaging, but hey, that's probably just me. Then I trim off any of the top parts that are also looking dry. The next cut I always do with leeks because it helps to clean them. I simply just split it down the middle, keeping the root whole so the leek stays together. Then I just cut across, keeping the slices reasonably chunky. You'll notice I haven't washed the leeks yet at all. They are as I bought them, and there is a reason for this. As you probably know, nine times out of 10, leeks have a ton of grit and dirt sandwiched between the layers. So this is how most chefs will go about preparing them. First, we cut them to get those parts that are hiding the dirt exposed, then dunk them into plenty of water like this. I like to go to town in this step to try and disturb the dirt and get it free from all of those layers. And if the recipe allows for it, I wash the leeks in two stages, and I'll show you what that second stage is in a moment. Now I just leave them to sit in water for 10 to 15 minutes to let the dirt settle to the bottom. But the most important thing here for me is that there's plenty of water, so the leeks are floating and not touching the base of the bowl. This is hard to show on camera, but what this means is the dirt can fall to the bottom and be separate from the leek. This is one of those little 1%s that makes a big difference. Okay, so now over to the stovetop, where I have a large pan of boiling water. Then I'm adding some salt, and this is the second cleaning stage, as well as being a cooking stage as well. It's the same principle as a bowl of water. I'm cooking them in plenty of water to give the dirt somewhere to settle below the leeks. I love steaming my veg for the health benefits, but for certain things, chefs have to choose boiling instead, because if I serve you gritty leeks in a restaurant, you're not gonna be too happy. So these steps may seem over the top, but they're fail-safes to ensure a good eating experience, because no one wants to eat gritty leeks. So I just scooped the leeks from the bowl of water and to leave as much of that grit at the bottom of the bowl. So I'm gonna cook these for five minutes, just to soften them slightly. They'll continue cooking later in the oven, so I don't need to worry about getting them perfect in this stage. After five minutes of cooking, I'm scooping them out with a slotted spoon rather than just pouring them through a colander, once again, to keep the dirt at the bottom of the pan. Don't worry, I'll stop talking about cleaning leeks now. As you probably can tell, I'm a little obsessive with it. They're going into a clean bowl of cold water, just to stop them cooking any further. In the spirit of keeping the washing up to a minimum, I'm gonna give this pan a quick rinse and put it straight back onto the heat, so I can use it for the sauce part of this recipe. The sauce is a bechamel base, otherwise known as a white sauce. For this recipe in particular, I'm using the times 10 rule, which means the same amount of butter and flour, then 10 times the amount of liquid, which will be milk. This will give me a slightly thicker sauce, but once it's mixed in with the leeks, it's the perfect consistency. So I'm gently melting 100 grams of butter. Once it looks like this, I add the flour, and I use a whisk or a spoon to mix it together. I'm gonna cook that out for a few minutes over a gentle heat, until I can smell something similar to the smell of cooked biscuits. I think this was Delia who first said this, and it's a yardstick I use whenever I'm making a roux-based sauce. Now, this next step is gonna trigger some people, but I want to show you how I guarantee a lump-free sauce whilst using cold, straight from the fridge milk. This is considered a lazy method amongst chefs, but there's method in my madness. Let me explain. With the pan on a low heat, I just add a dash of milk, probably around 100 mil. Let it heat on the base of the pan for a moment and stir it in until it's a smooth consistency. Then I add the next batch of milk, a little more than last time, around 150 mil. Give that some time to come up to temperature. I've taken a lot of the heat out of the base of the pan with the first round of milk. So from here, I give it around 30 seconds to get warm before gently whisking it in. Then I just repeat this process, gradually increasing the amount of milk I add each time, letting it heat up for as long as it needs. I just look for a little bubbling around the edges. Then I whisk it in. Before the pitchforks come for me, I'm a big advocate for making this sauce the traditional way by heating the milk and infusing it with some sort of flavor, then stirring it with a wooden spoon only, no whisk. But there's enough flavors going on in this recipe. Once everything's mixed together, it's a very flavorful dish. So for this recipe, I say take the easy path and save yourself some time and dishes. And I decided to use a whisk because I think it's how a lot of you will do it at home. Either way, spoon or whisk, the method is exactly the same. Okay, so that's all the milk. I'm gonna leave this cooking on a low heat for another 15 minutes to cook out the flour and get it to the thickness that I'm looking for. And I'll check on it every five minutes or so, just to make sure it's not catching on the base of the pan. 15 minutes later, this sauce is ready. It's thickened up and it's smooth with no lumps at all. I'm gonna finish this sauce off the heat and I'll explain why in a moment. So first in goes a heaped teaspoon of whole grain mustard. If you don't like mustard, then I'm gonna encourage you to try it anyway. Mustard really helps to lift the flavor of cheese, particularly cheddar cheese. The goal isn't to taste mustard in the sauce, it's to taste more of a depth of the cheese flavor. Then I'm adding some salt, a little cracked black pepper, and finally the grated cheese. I'm using a mature cheddar, also known as a sharp cheddar. The stronger the flavor of the cheese, the better this sauce will be. And for my British audience, I know this doesn't look like our typical mature cheddar. I'm not filming this in the UK and finding our beloved crumbly cheddar cheese outside of the UK is easier said than done. This is the closest thing I could get my hands on. Now, the reason I'm mixing all of this off the heat is because cheese splits really easily if it's exposed to heat. This isn't necessarily true for cheese with emulsifying agents, but for traditional cheddar cheese, it is a risk, particularly for the strong ones. So there's enough residual heat in this sauce to easily melt the cheese. This is something I got taught in my first year in a professional kitchen, and it's something I've never not done. Give it a taste, make sure you're happy with the seasoning and flavors, then simply just add the leeks to the saucepan. These have just been drained from the water once they were cool. Mix them really well so everything's as even as possible. Then into an ovenproof dish of some sort. And from here, you can either bake it in the oven straight away until the top is golden brown, or you can chill it and cook it over the next couple of days. I'm gonna assume most of you are gonna do the second option, so that's what I'll do as well. I'm gonna cover it and put it in my fridge and finish the recipe tomorrow. It's the next day, and this cheese and leek bake is ready to be baked. Nothing has really changed overnight, except it's set a lot more. So I'm placing it into my oven that's set at 180 Celsius. How long this takes to bake is gonna be a massive variable. If it's alone in the oven and it's come straight from the fridge, I would give it at least an hour. If the oven is busy and it has other things being roasted and the door is being opened and closed regularly, then I would give it an hour and a half. I wish you could smell this. It's tasty, creamy, flavorful, and it always gets great comments around the dinner table. The beauty of this dish is it holds the heat really well. This came out of the oven an hour and a half ago, and it's still hot enough in the middle to serve straight to the table. I just covered it with a tray and I left it to sit on the side. Check this video out next for another recipe to impress your friends and family.