I started making these because I had half a loaf of sourdough going stale and a container of mushrooms that needed using. Not exactly a glamorous origin story. But the combination — brown butter mushrooms, good melty cheese, thick toast — turned out to be one of those recipes I keep coming back to on weeknights when I want something that feels a little special without actually trying that hard.
The brown butter is the thing. It takes maybe four extra minutes compared to just melting butter, and the payoff is enormous. Nutty, almost caramel-y, and it coats the mushrooms in a way that regular butter just doesn’t. I do it in a small pan on the stove while the toaster oven preheats — no extra dishes, no drama. If you don’t already have a decent toaster oven baking tray that fits your oven snugly, it’s worth grabbing one. The thin, flimsy ones that came with mine always wobbled and I’d lose half my toppings.
Gruyère is my strong preference here. It melts beautifully and has that slightly funky, nutty flavor that goes with mushrooms way better than mozzarella ever could. That said, if you only have Swiss in the fridge, go for it. A good box grater makes quick work of it — freshly grated really does melt better than the bagged stuff, and for a recipe this simple, those details matter.
These work as a light dinner with a green salad, or honestly just on their own. Four slices disappears fast if there are two of you.
Toaster Oven Crispy Brown Butter Roasted Mushroom and Gruyère Tartines with Fresh Thyme
Thick slices of crusty bread topped with nutty brown butter mushrooms, melted Gruyère, and fresh thyme. Ready in about 25 minutes and honestly way better than it sounds.
Ingredients
Instructions
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Preheat your toaster oven to 425°F. If it has a broil+bake or convection setting, use it — if not, regular bake is totally fine.
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Set a small skillet on the stovetop over medium heat. Add the butter and let it melt, then keep going. Swirl it a few times. It'll foam up, then the foam settles down and you'll start to see little brown bits at the bottom and smell something nutty. That's the move. Pull it off the heat right around 3-4 minutes — it can go from brown to burnt fast.
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Add the mushrooms to the brown butter right in the pan over medium-high heat. Don't stir them for the first 2 minutes. Let them sit and get some color. Then stir, add the garlic, thyme, and soy sauce, and cook another 2-3 minutes until most of the liquid has evaporated. Season with black pepper and taste for salt.
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Brush the bread slices lightly with olive oil on both sides. Arrange them on your toaster oven's baking tray and toast at 425°F for about 4-5 minutes until just starting to get golden.
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Pull the tray out. If you're using Dijon, spread a thin layer on each slice now. Pile the mushrooms generously on top of each piece — don't be shy — then scatter Gruyère over everything.
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Put the tray back in and bake another 6-8 minutes until the cheese is melted, bubbly, and getting a little golden in spots. If your toaster oven has a broil function, hit it for the last 60-90 seconds for extra color on the cheese. Watch it — broil moves fast.
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Finish with a pinch of flaky sea salt and a few fresh thyme leaves. Eat immediately. These don't wait well.
Notes
Mushrooms: cremini are the go-to but any mix works — shiitake adds a nice chewiness and oyster mushrooms get almost meaty. Don't crowd the pan when you cook them or they'll steam instead of brown. If you don't have Gruyère, Swiss or even sharp white cheddar is a solid substitute, just different vibes. The soy sauce sounds weird but it just adds depth — you won't taste it as soy. Leftovers are rough honestly; the bread softens overnight. If you have leftover mushrooms though, they keep fine in the fridge for 3 days and are great on eggs.
Nutrition
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Written by
Emma is a home cook who loves coaxing big flavor out of a toaster oven — from crispy roasted vegetables to easy weeknight dinners and sweet treats. She develops and tests Toastera's recipes for small-appliance kitchens.
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