These mushroom and fontina baguette slices started as something I threw together on a Tuesday when I had half a baguette going stale and a container of mushrooms that needed using. That’s still basically what they are. But browning the butter first — really letting it get nutty and almost toasty — changes everything about how the mushrooms taste. They pick up this deep, savory quality that makes the whole thing feel a lot more intentional than it actually is.
The toaster oven is genuinely the right tool for this. You get the bread crisping up from below while the broiler handles the cheese on top, which is harder to pull off in a full-size oven without constantly repositioning things. If you don’t already have a toaster oven baking sheet that fits your machine, it’s worth grabbing one — a half-sheet pan won’t fit most standard toaster ovens, and the right pan makes broiling way less stressful.
I use cremini mushrooms here because they have more flavor than white buttons and they’re at every grocery store. A small splash of soy sauce in the pan sounds odd but it just deepens everything — you won’t taste it as soy sauce, it just makes the mushrooms taste more like themselves, weirdly enough. Fresh thyme is worth it. Dried thyme, if that’s what you’ve got, use half the amount.
This works equally well as a starter for a dinner party (people always go for them immediately) or as a lazy dinner with a salad alongside. If you’re working with a compact toaster oven, just do the baguette slices in two batches rather than crowding the pan.
Toaster Oven Crispy Brown Butter Roasted Mushroom and Fontina Stuffed Baguette Slices with Fresh Thyme
Thick baguette slices loaded with garlicky brown butter mushrooms and melted fontina, broiled until golden and bubbling. Ready in about 25 minutes and honestly better than anything you'd order at a bar.
Ingredients
Mushrooms
Baguette
Instructions
Brown the Butter and Cook the Mushrooms
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Set your toaster oven to 425°F on the bake setting and let it heat up fully.
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While it heats, put a small skillet over medium heat on the stovetop and add the butter. Let it melt and keep going — swirl it occasionally. After about 3 minutes you'll see brown flecks forming and it'll smell nutty. Pull it off the heat for 30 seconds.
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Return the pan to medium-high. Add the mushrooms in a single layer and don't touch them for 2 minutes. Let them get some color. Stir, add the garlic and thyme, and cook another 3 minutes until the mushrooms are golden and any liquid has cooked off.
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Add the soy sauce and lemon juice, stir quickly, and season with salt and pepper. Take off the heat.
Assemble and Toast
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Arrange your baguette slices on a toaster oven baking sheet. Brush each one lightly with olive oil.
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Bake for 5 minutes until the bread is just starting to get crisp on the edges.
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Pull the pan out. Spoon the mushroom mixture generously onto each slice — pile it on, don't be shy. Top with fontina, then a little Parmesan, and a pinch of red pepper flakes if you want.
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Switch your toaster oven to broil. Slide the pan back in and broil for 3-4 minutes, watching closely the whole time, until the cheese is melted, bubbling, and has some golden-brown spots on top.
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Scatter fresh thyme over everything and serve immediately. They go fast.
Notes
Fontina melts beautifully but if you can't find it, Gruyère or provolone both work well here. Don't skip browning the butter — it's what makes the mushrooms taste almost meaty. If your toaster oven's broiler runs hot (mine does), check at 2 minutes. Leftovers reheat decently at 375°F for 5 minutes, though the bread loses some crunch. For a slightly heartier version, add a thin smear of whole grain mustard to the bread before topping.
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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