Delicious and make-ahead-able, this Creamy Mushroom and Gruyere Casserole is perfect for Thanksgiving, Christmas or for entertaining any time of year. It’s also easy enough for family dinners, too!
Here in Canada, we celebrated our Thanksgiving back in mid-October, but I’d have to be living under a rock though not to realize that American Thanksgiving is fast approaching. I empathize with those of you scrambling to finalize your menu and get your grocery shopping planned and done! So to that end, I thought I’d offer up a little something – hoping it might be helpful for anyone looking for one more dish to round-out their special meal.
If your family is like my family, there are certain things that will always show up on the Thanksgiving table. In my family, it’s turkey and gravy, of course, my Mom’s make-ahead mashed potato casserole (with cream cheese and sour cream) and traditional bread/sage stuffing. After that, it tends to change up a bit every year. Sometimes we have soup. Sometimes salad. And there’s always a few vegetable dishes of some sort. It seems every year though I’m always looking for just one more dish. I think this mushroom dish fits that bill perfectly! It’s different from the usual, easy to make (and make ahead), re-heats quickly and has flavours that everyone will love
This mushroom side dish features sauteed leeks and a creamy sauce flavoured with a bit of grainy mustard and lemon juice. The lemon juice is the perfect touch of acidity that heightens the flavours and prevents this dish from becoming overly rich. On top, is a crispy topping made from fresh bread crumbs (just throw a couple of slices of bread in a food processor) and some Gruyere cheese. It doesn’t have a ton of cheese. Gruyere has loads of flavour, so a little goes a long way. It’s the perfect complement to the mushrooms.
Of course, it goes without saying that this dish would also be perfect any time of year – for entertaining, or next to simple grilled chicken, pork or beef for any meal at home. It comes together quickly and is sure to become a family favourite.
Get the Recipe: Creamy Mushroom Leek and Gruyere Casserole
- 5 Tbsp. butter, divided
- 1 stalk leek, (white and light green parts only), halved lengthwise and then sliced crosswise
- 1/2 tsp. each salt and pepper
- 3 8 oz pkgs cremini and/or button mushrooms, sliced
- 1/3 cup all-purpose flour
- 1 1/4 cups chicken broth, or sub vegetable broth to keep it vegetarian
- 1/2 cup whipping cream 35%
- 2 Tbsp. grainy Dijon mustard
- 1/2 cup chopped fresh parsley
- 1 Tbsp. chopped fresh thyme
- 4 tsp. lemon juice
Gruyère Crumb Topping:
- 2 cups fresh bread crumbs, slightly stale bread, processed in food processor
- 3/4 cup grated Gruyère cheese
- 2 Tbsp. butter, melted
- 2 Tbsp. chopped fresh parsley
- In a large skillet, melt 1 Tbsp. of the butter over medium heat. Cook leeks and half each of the salt and pepper, stirring often, until leeks are softened, about 6 minutes. Remove to bowl and set aside.
- In the same skillet, melt the remaining 3 Tbsp. butter over medium heat. Cook mushrooms with the remaining salt and pepper, stirring occasionally, until mushrooms are just tender and have released their juices, 5 to 8 minutes. Sprinkle with flour and cook, stirring, until light golden, about 2 minutes. Return the leeks to the pan.
- Whisk in broth, cream and mustard until smooth. Cook, whisking, until thickened, 3 to 5 minutes. Stir in parsley, thyme and lemon juice. Spoon into shallow 8-cup casserole dish. (Make-ahead: Let mushrooms cool to room temperature, then cover and refrigerate for up to 24 hours. To reheat, cover with foil and bake in 375° F. oven until hot and bubbly, 40-50 minutes. Uncover and continue with recipe. You can also mix together the crumbs and cheese of the crumb topping and refrigerate ahead. When ready to broil, stir in parsley and melted butter.)
- Gruyère Crumb Topping: In bowl, stir together bread crumbs, Gruyère cheese, butter and parsley. Sprinkle over mushroom mixture. Broil until topping is golden, 2 to 4 minutes.
Hi! I’m Jennifer, a home cook schooled by trial and error and almost 40 years of getting dinner on the table! I love to share my favourite recipes, both old and new, together with lots of tips and tricks to hopefully help make your home cooking enjoyable, stress free, rewarding and of course, delicious!
Does this dish freeze well? Many thanks, D
Hi Donna, I don’t think I’ve ever tried freezing this one. Mushrooms can be tricky to freeze/thaw, so I’m not sure how well it would do. I think if you try it, I would probably re-heat from frozen, so the extra moisture cooks off in the oven, rather than settling in the dish.
Delicious. Thank you.
Glad you enjoyed it, Donna :) Thanks!
It does. Thank you. Off to look at the quiche recipes . . .
I am cooking my way through your Web site. Your recipes are fabulous, Jennifer. All are keepers. Now, a question: I am in need of a brunch dish? Would this work with eggs? And if so, cooked should I cook them? Thank you so much.
Apologies for the incoherent sentence – I was typing too fast. If I serve eggs, how should I prepare the eggs? Scrambled? Sunny-side up? Thanks, D
No worries :) This is quite a rich dish and while it could work with eggs, you might find it a bit heavier than you want for brunch. If you’re thinking eggs, I’d maybe have a look at my Quiche Lorraine (my favourite special occasion brunch dish!) or something a little lighter like my Asparagus Quiche with Hashbrown Crust. I love to serve quiche with a bright, fresh salad and maybe something like Baked Tomato halves with a bit of Parm and bread crumbs on top. Just thinking out loud :) Hope that helps!
Do you bake it at the same temperature and time if you are not doing make ahead?
Yes you do, Sara :)
This recipe is fantastic. Served it with a skirt steak and hasselback potatoes. The family loved it. Definitely will be added to my recipe box.
So glad you enjoyed it, Cathy. Would be lovely with steak!
This looks absolutely amazing, a great idea for Christmas. Both my kids refuse to eat mushrooms, so I am glad to have found a mushrooms side dish to serve separately from the stuff they do eat. Love this!
Thanks so much Adina. I think they would love this dish :)
Mmmm…this gratin is calling my name! I’m a big mushroom and leek lover. And of course – cheese and breadcrumbs are always amazing too! This is the perfect addition to Thanksgiving!
Thanks Liz. The topping on this one was especially awesome! Have a great Thanksgiving. Jealous of all you American turkey eaters this week ;)
Oh My goodness, this looks amazing, I now have my last side planned!
Thanks s0 much, Cheri! Have a great Thanksgiving :)
This looks insanely good! I just want to reach through my screen and grab it.
Thanks Jennifer. Wouldn’t it be great if that were possible ;)
I love this gratin, it looks so cozy and comforting!
Thanks Laura :)
Wow Jennifer – I love this dish! I adore mushrooms anyway and leeks are becoming more and more present in my cooking. If my family would not disown me, I’d make this for Thanksgiving! Perhaps I can talk them into Christmas. Lovely dish – thank you!
Thanks Tricia :) I know what you mean about being disowned if you switch up dishes. This one is easy enough for any time though, so you can easily enjoy after Thanksgiving :)
This gratin is absolutely beautiful and it looks seriously delicious! Loving the gruyere, leek and thyme paired with the mushrooms! Perfectly elegant, but easy enough for any gathering! Pinned! Cheers and thanks for sharing the YUM! :)
Thanks so much, Cheyanne and thanks for pinning :)
Jennifer, you have outdone yourself with this one! I just saw your photo on IG and had to come right over to the blog and check this recipe out! You are totally right, this dish would be perfect for holiday dinners AND any time of year too! My husband Tom is going to LOVE this one too!! Spectacular!
Thanks Mary Ann. We love this dish and I don’t wait for holidays to make it ;)
Like you, we’ve already had Thanksgiving but booooooy could I go for a pan of this right now! So inviting! Also, I love stuff like this as the main dish too. With a side salad I am good to go!
That’s true, Katrina. I don’t often think about vegetable dishes as mains. Though I would totally enjoy this with a salad, I fear my husband would be left looking around for the rest of the meal ;)
Mmm I love gruyere gratins! I totally want to make this for Thanksgiving! This looks delicious!
Thanks Linda. I’m sure you would enjoy it! :)