This creamy mushroom gratin recipe features tons of sautéed leeks and wild mushrooms baked in the silkiest cream sauce that is both naturally vegan and gluten free (without flour or butter). For that coveted je ne sais quoi “gratinee” element make sure to top with a sprinkling of our easy crispy bread crumb topping included below.
Champignons au gratin or the French way of saying delicious creamy mushroom casserole with a crispy top (cheese or breadcrumbs or both). A traditionally indulgent Christmas casserole featuring delicious and individually layered seasonal vegetables. It could be a starter, an entree in its own right served alongside a potato dish with spinach, a meatless roast or our fan favorite vegan chicken.
About the Mushrooms
Before I dive into any details, just know you can make this dish with any mushrooms you like! That being said, wild mushrooms are popping up at the farmer’s market stands this time of the year so this is definitely your moment to explore the incredibly delicious world of Fungi! I get giddy over Chanterelle season, to me there really isn’t any mushroom out there quite like a frilly yellow footed chanterelle. They have a meaty texture with a woodsy but delicate aroma subtly reminiscent of apricot and come in a range of sizes, from a couple of inches to the size of your hand.
Because chanterelles are wild there will be plenty of pine needles, moss and dirt to clean. This is a mushroom that must be washed and that is absolutely fine, don’t fret. Rinse each one individually with the shower spray if available and place on a lint free tea towel to dry. Really, it’s fine, just think of all the forest rains they have already been through.
The important thing is to choose a mushroom variety you know you love. For example, Maitake also known as hen of the woods has a very different flavor than chanterelles or porcini. It’s meaty but funky, so make sure you are into that deep earthiness before using it in a dish such as this. Shiitakes, oysters and cremini are commonly found year round and would work great in this recipe any night of the week.
I would argue that this is just as much a leek gratin as it is a mushroom casserole. Cook them down until completely collapsed and start to get a little color to bring our their natural sweetness. It’s important that you clean them very well first as they are notorious for capturing lots of sandy soil in between their layers. Best way to deep clean Is to thinly slice the leeks first (white and green parts), place in a large bowl and cover with cold water. Give them a good stir and allow to sit for a few minutes. All the leeks will float to the top while the dirt will sink to the bottom. You can transfer them straight into a hot dry skillet and all that moisture will evaporate while they cook actually helping with the sautéing process. Easy peasy!
Gratin Cream Sauce
It’s vegan, amazing, made from cashews, dairy free + gluten free and comes together in the blender in a few minutes. If using a powerful blender such as a Vitamix it can all go straight in, otherwise it’s important to soak or boil the cashews for 20 minutes in hot water before blending. The consistency of the sauce will be that of thin cream, extra smooth and silky that will thicken up and set during baking.
Bread Crumb Topping
This is the same bread crumb toping I use for our vegan mac and cheese and it really elevates a dish to the next level. The crunch balances the creaminess of the casserole like a symphony! Basically pan fried fresh herbs like sage or thyme, panko bread crumbs toasted around until golden and finished with a pinch of sea salt flakes. I like to prepare this on the stovetop in its own skillet versus just sprinkling over the casserole and baking. Trust me, It’s better this way!
Recipe Tips + Variations
- Swaps – Instead of leeks you could opt for equal amounts of green onions, thinly sliced fennel bulb, zucchini and even artichoke hearts. Cooked rice, farro or barley could be used as layer, I highly encourage you to experiment with different variations.
- Potatoes – thinly sliced golden potatoes can be used to layer the bottom of the dish. If going this route make sure to use a mandolin on the thinnest setting, you should be able to read the morning paper through them. You could also layer the top before adding the cream sauce, in this case make sure to bake your gratin for a full hour to ensure the potatoes are fully cooked.
- Make Ahead – All the ingredients can be prepped ahead and assembled in the casserole but store the Cream separately in the refrigerator until ready to bake.
- Leftovers Storage + Reheating – If you happen to have any leftovers at all simply refrigerate in a lidded container up to 5 days. You can quickly microwave to reheat or place the casserole covered in a 350″F oven for 20 to 30 minutes until hot in the center.
how to make mushroom gratin (Dauphinoise)
Leek Mushroom Gratin
- 4 cups leeks 2-3 medium leeks
- 1 lb wild mushrooms (cleaned and dried: chanterelles, lobster mushrooms, chicken of the woods, oyster mushrooms)
- 1 large garlic clove minced
- 1/4 cup dry white wine or a squeeze of lemon
- 1 Tbsp fresh thyme leaves
- Olive oil as needed
Cashew Cream Sauce
Bread Crumb Topping
- 1.5 cup panko breadcrumbs
- 1.5 Tbsp olive oil
- 1 Tbsp fresh herbs like thyme or sage
- 1 pinch sea salt flakes
Prepare the Leeks
- Thinly slice the leeks and add them to a large bowl. Cover with cold water and give them a good stir. Allow to sit for a few minutes for all the sand and grit to fall to the bottom.4 cups leeks
- Preheat a large heavy bottom skillet over medium high heat. Using your hands scoop the leeks from the water and add them to the dry hot skillet. Sautee until all moisture has evaporated.4 cups leeks
- Drizzle the leeks lightly with olive oil and season with a pinch of sea salt. Stir well and continue sautéing until the leeks have completely wilted and start to get some color.Olive oil as needed
- Lightly oil a 10 inch round baking dish or line with parchment paper. Spread the cooked leeks in one layer on the bottom of the dish and set aside.4 cups leeks
Cook the Mushrooms
- Rinse and dry the mushrooms on a lint free tea towel. (Depending on the variety used you might want to tear them into smaller pieces, half them or use whole). Add the mushrooms to the same skillet you cooked the leeks in and turn up the heat. Sautee long enough at relatively high heat so all the water released by the mushrooms evaporates (sometimes mushrooms release a lot of water sometime none at all). Stand by!1 lb wild mushrooms
- Push the mushrooms to the sides of the skillet and add a drizzle of olive oil in the center. Add the minced garlic and cook until the fragrant. (Do not burn the garlic.1 large garlic clove, Olive oil as needed, 1 Tbsp fresh thyme leaves
- Stir well then add the white wine and thyme. Continue cooking until the wine has evaporated. Season the mushrooms with a small pinch of salt, remove from heat and transfer to the casserole with the leeks. Spread in an even layer.1/4 cup dry white wine
Preheat your oven to @375”F
Make the Cashew Cream
- Add the cashew pieces, water, nutritional yeast, onion powder and salt to a very powerful blender such as a Vitamix. (If a less powerful blender is used, make sure to soak (or boil) the cashews in advance for 20 minutes in hot water before processing. Blend until creamy smooth.1 cup raw cashew pieces, 1.5 cups water, 2 Tbsp nutritional yeast, 3 tsp onion powder, 3/4 tsp salt
- Pour the cashew cream over the mushrooms and leeks and give it a little shake to evenly distribute. Cover with aluminum foil and transfer to the preheated oven. Bake the casserole for 45 to 50 minutes until the cream has set and thickened. Sprinkle with the crispy bread crumbs and serve hot.1 lb wild mushrooms, 4 cups leeks
Crispy Bread Crumb Topping
- Preheat a 10 inch skillet with 1.5 Tablespoon of olive oil over medium heat. Add the herbs and fry until crispy. Stir in the bread crumbs and toast moving them around until golden brown all over taking care not to burn them. Remove from heat and a dd a pinch of sea salt flakes.1.5 cup panko breadcrumbs, 1.5 Tbsp olive oil, 1 Tbsp fresh herbs like thyme or sage, 1 pinch sea salt flakes
Plantricious + WFPB
- To make the casserole compliant make sure to omit all oil or replace with water or veggie stock as needed.
- Swaps - Instead of leeks you could opt for equal amounts of green onions, thinly sliced fennel bulb, zucchini and even artichoke hearts.
- Potatoes - thinly sliced golden potatoes can be used to layer the bottom of the dish. If going this route make sure to use a mandolin on the thinnest setting, you should be able to read the morning paper through them. You could also layer the top before adding the cream sauce, in this case make sure to bake your gratin for a full hour to ensure the potatoes are fully cooked.
- Make Ahead - All the ingredients can be prepped ahead and assembled in the casserole but store the Cream separately in the refrigerator until ready to bake.
- Leftovers Storage + Reheating - If you happen to have any leftovers at all simply refrigerate in a lidded container up to 5 days. You can quickly microwave to reheat or place the casserole covered in a 350"F oven for 20 to 30 minutes until hot in the center.
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