Wild Mushroom–Green Olive Gratin Toasts: My Winter Bistro Bite (With a California Wink)
I came up with these Wild Mushroom–Green Olive Gratin Toasts on one of those damp, moody winter nights when California pretends it’s Paris. I wanted the feeling of a bistro snack—hot toast, something bubbling under the broiler, a glass of nervy natural white—but I also wanted lift. Not heaviness. Not a cream-bath.
The inspiration is half French technique, half my farmers’ market habits: a skillet of jammy wild mushrooms (don’t rush them—let them go bronzed and glossy), the briny pop of green olives, then a cheesy gratin “lid” that puffs and blisters like it owns the place. The preserved-lemon crème fraîche is my little West Coast rebellion: salty citrus, a whisper of mustardy snap, and suddenly the whole thing tastes awake.
A memory: I first served a version of this at a last-minute dinner with friends—everyone perched in the kitchen, tearing toast like we were at a Paris zinc bar, except someone had brought avocados because… of course.
Make it your own: swap in whatever mushrooms look handsome, add thyme or chile flakes, or finish with a jammy egg. And please—butter the toast like you mean it.
Featured Recipe
Wild Mushroom–Green Olive Gratin Toasts with Preserved-Lemon Crème Fraîche + Quick Dressed Arugula
This is my winter bistro bite when I want briny + bright without doing the whole seafood-tower song and dance: jammy wild mushrooms baked under a bubbly, cheesy gratin lid, spooned over garlicky toast. I finish it like a Californian who trained in Paris—preserved lemon, a little mustardy snap, and a quick, peppery salad right on top so every bite feels lifted.
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Ingredients
- 450 g Mixed wild mushrooms (oyster, maitake, chanterelle, or cremini), torn/sliced(Aim for a mix of textures; avoid washing—brush/trim instead)
- 1 tsp Kosher salt(Plus more to taste)
- 1/2 tsp Black pepper
- 2 tbsp Unsalted butter(Because we’re civilised)
- 1 tbsp Olive oil
- 2 Shallots, finely sliced
- 2 cloves Garlic, finely grated or minced
- 1 tsp Fresh thyme leaves(Or 1/2 tsp dried)
- 120 ml Dry white wine or dry vermouth(Natural wine is welcome at my house)
- 120 ml Crème fraîche(Sour cream works in a pinch)
- 1 1/2 tsp Dijon mustard
- 1 tbsp Preserved lemon peel, finely chopped(Rinse if very salty; substitute 1 tsp lemon zest + 1 tsp lemon juice)
- 70 g Castelvetrano olives, chopped(Or any buttery green olive)
- 90 g Gruyère, coarsely grated(Comté works too)
- 25 g Parmesan, finely grated
- 35 g Panko breadcrumbs(For the gratin crunch)
- 1 tbsp Lemon juice(Plus more to taste)
- 60 g Arugula(Or baby mustard greens)
- 2 tbsp Extra-virgin olive oil(For dressing + finishing)
- 1 1/2 tbsp Sherry vinegar or white wine vinegar
- 1/2 tsp Honey(Just to round the acid)
- 8 slices Baguette or country loaf, sliced(About 1.5 cm thick)
- 1 clove Garlic clove, halved (for rubbing toast)
Instructions
- 1
Heat the oven to 220°C / 425°F. Place 4–6 small gratin dishes (or one 20 cm / 8-inch baking dish) on a sheet pan for easy handling.
5 min
Tip: If you’ve got convection, use it—this is a gratin, not a spa day.
- 2
Toast the bread: brush 8 slices Baguette or country loaf, sliced lightly with 1 tbsp Olive oil, bake 6–8 minutes, flipping once, until crisp and golden. While hot, rub with 1 clove Garlic clove, halved (for rubbing toast). Set aside.
8 min
Tip: Garlic-rubbed toast is the bistro trick that makes people think you tried harder than you did.
- 3
Cook the mushrooms (properly): heat a large skillet over high heat. Add 1 tbsp Olive oil and 2 tbsp Unsalted butter. Add 450 g Mixed wild mushrooms (oyster, maitake, chanterelle, or cremini), torn/sliced and 1/2 tsp Kosher salt; spread them out and let them sear without stirring for 2 minutes. Toss, then continue cooking until deeply browned and the pan is mostly dry, 6–8 minutes more.
10 min
Tip: If your mushrooms are steaming, your pan is too crowded—work in batches if needed.
- 4
Add 2 Shallots, finely sliced, 2 cloves Garlic, finely grated or minced, and 1 tsp Fresh thyme leaves; cook until the shallots soften and turn glossy, about 2 minutes. Pour in 120 ml Dry white wine or dry vermouth and boil hard until reduced by about half, 2–3 minutes.
5 min
Tip: That quick reduction is your ‘sauce’—all the flavor, none of the heavy cream nap.
- 5
Turn off the heat. Stir in 120 ml Crème fraîche, 1 1/2 tsp Dijon mustard, 1 tbsp Preserved lemon peel, finely chopped, and 70 g Castelvetrano olives, chopped. Taste and adjust with 1/2 tsp Black pepper and 1 tbsp Lemon juice if you want it brighter.
2 min
Tip: You’re balancing earthy (mushroom) with briny (olive) and bright (lemon). Trust your tongue.
- 6
Assemble the gratin: divide mushroom mixture into dishes. Toss 90 g Gruyère, coarsely grated, 25 g Parmesan, finely grated, and 35 g Panko breadcrumbs together, then sprinkle evenly over the top. Drizzle with a little 2 tbsp Extra-virgin olive oil.
5 min
Tip: A little oil on the crumbs = the kind of crunch people fight over.
- 7
Bake until bubbling and deeply golden, 10–12 minutes. If you want extra color, broil for 30–60 seconds at the end—watch like a hawk.
12 min
Tip: Gratins go from ‘perfect’ to ‘why is it black?’ in one sip of wine.
- 8
Meanwhile, dress the greens: whisk 1 1/2 tbsp Sherry vinegar or white wine vinegar, 1 tbsp Lemon juice, 1/2 tsp Honey, 2 tbsp Extra-virgin olive oil, and a pinch of salt. Toss with 60 g Arugula right before serving.
3 min
Tip: Dress at the last second so it stays perky, not sulky.
- 9
Serve: put garlic toast on each plate, spoon on (or tuck beside) the bubbling mushroom gratin, and crown with a small tangle of dressed arugula. Finish with a final squeeze of lemon if you like living deliciously.
2 min
Tip: The greens aren’t a side—they’re the bright, peppery ‘reset’ between bites.
Chef's Notes
This one reminds me of a February night in Oakland when it was raining sideways and I needed something that felt like a Paris bar snack—warm, cheesy, deeply savory—but with California energy. The preserved lemon is my little sunbeam, and the arugula salad on top is non-negotiable: it keeps the whole thing flirtatious instead of sleepy. Wine pairing: a salty, citrusy skin-contact white or a light chillable red (Gamay, Trousseau) that won’t bully the mushrooms.
Marguerite Lavigne
French soul, California sun
I grew up in a small village outside Lyon, where my grandmother taught me that the best meals come from respecting your ingredients. After training at Le Cordon Bleu and spending years in Parisian kitchens, I moved to San Francisco and fell in love with California's farmers markets and wine country. Now I cook the food I wish my grandmother could taste—French technique with California abundance, where a perfect roast chicken might come with Meyer lemon and wild fennel instead of tarragon.