Mushroom & Onion Galette

I adore how this galette combines caramelized onions, sautéed mushrooms, creamy cheese, and a crisp puff pastry crust—finished with peppery arugula and a tangy balsamic drizzle. It’s elegant enough for a dinner party, yet cozy for a weeknight.

Why You’ll Love This Recipe

I love that this recipe is super flexible—using store‑bought puff pastry saves time, and I can substitute cheeses or mushrooms based on what I have. The caramelized onions and mushrooms bring deep flavor, while the cheese and balsamic reduction add richness and brightness.

ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

• 2 Tbsp unsalted butter

• 8 oz shiitake mushrooms, quartered

• 8 oz white button mushrooms, quartered

• 8 oz mini portobello mushrooms, quartered

• 1 large red onion, thickly sliced

• ½ tsp kosher salt

• ½ tsp black pepper

• 3 sprigs fresh thyme, leaves removed

• 3 cloves garlic, minced

• flour for dusting surface

• 1 puff pastry sheet, thawed to room temp

• 4 Tbsp garlic‑&‑herb Boursin cheese, room temp

• 1 cup shredded gruyère or smoked gouda (divided)

• Egg wash: 1 egg, beaten

• Balsamic reduction: ½ cup balsamic vinegar + 3 Tbsp sugar

• Garnish: 1½ cups arugula tossed with 1 tsp extra‑virgin olive oil

directions

1. Preheat oven to 400 °F. Melt butter in a large saucepan over medium‑high. Add onions and mushrooms, cook ~10–15 min until most liquid evaporates.

2. Add salt, pepper and thyme. Continue reducing ~10 min. Stir in garlic, cook 2–3 min until fragrant. Remove from heat, mix in ½ cup shredded cheese, then let cool.

3. Lightly flour work surface; roll puff pastry to fit your baking sheet. Transfer it to the pan.

4. Spread Boursin in the center, leaving ~2 inches around edges. Top with mushroom‑onion filling. Fold edges over filling.

5. Sprinkle remaining ½ cup cheese on top. Brush crust with egg wash. Bake 40 min or until golden and crisp. Transfer to a rack; let cool 10 min.

6. While baking, make balsamic reduction: simmer vinegar + sugar in skillet over medium‑high until thickened, ~10 min. Remove from heat.

7. Toss arugula with olive oil. When galette is slightly cooled, top with arugula and drizzle balsamic reduction.

Servings and timing

I get about 8 generous slices.

• Prep: ~15 min

• Cook: 40 min bake + ~20 min filling & reduction

• Cooling & assembly: ~15 min

• Total: ~1 hr 30 min

Variations

• Swap puff pastry for pie dough.

• Try goat cheese or cream cheese instead of Boursin.

• Use different mushrooms—cremini, chanterelles, morels.

• Make it vegan: use vegan pastry, omit cheese or use plant-based cheese, and replace butter with olive oil.

storage/reheating

• Refrigerate cooled galette in an airtight container up to 3 days.

• Reheat in a preheated 350 °F oven for 10–15 min until warmed and crust crisp again.

FAQs

How do I clean mushrooms properly?

I gently wipe mushrooms with a damp paper towel or give them a quick rinse and pat dry—never soak them, or they’ll get soggy.

Can I make the balsamic reduction ahead?

Yes! I make it up to 3 days ahead, store in the fridge, and rewarm or drizzle it straight on.

What cheese substitutes work well?

I’ve swapped goat cheese, cream cheese, or even ricotta for Boursin. For topping, gruyère, smoked gouda, or fontina all melt beautifully.

Can I freeze the galette?

Absolutely. I freeze baked, cooled galette wrapped tightly for up to 1 month. To reheat, I thaw overnight and rewarm in a 350 °F oven for ~15–20 min.

Is this galette gluten‑free?

You need a gluten‑free puff pastry or make a crust using almond or gluten‑free flour to adapt. The filling is naturally gluten‑free.

Conclusion

This Mushroom & Onion Galette is one of my favorite dishes when I want something comforting yet elegant. The combination of caramelized layers, creamy cheese, and crisp pastry is always a hit. I encourage you to make it your own—with different mushrooms, cheeses, or crusts—to suit your taste. Enjoy!

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