Caramelized Onion & Gruyère Galette with Honey-Thyme Glaze

A rustic free-form tart with a shatteringly flaky, buttery crust that cradles deeply caramelized onions and nutty Gruyère — finished with a fragrant honey-thyme glaze that pulls sweet and savory into perfect balance. It looks effortlessly impressive and tastes even better than it looks.

Ingredients

• all-purpose flour – 1½ cups
• kosher salt – ½ teaspoon
• granulated sugar – 1 teaspoon
• unsalted butter, very cold, cut into ½-inch cubes – 10 tablespoons (1¼ sticks)
• ice water – 3–5 tablespoons

• unsalted butter – 2 tablespoons
• olive oil – 1 tablespoon
• large yellow onions, thinly sliced – 3 (about 5 cups sliced)
• kosher salt – ¾ teaspoon
• fresh thyme leaves – 1 tablespoon
• dry white wine or dry sherry – 2 tablespoons
• black pepper, freshly cracked – ¼ teaspoon
• Gruyère cheese, finely grated – 1½ cups

• large egg – 1
• whole milk – 1 tablespoon
• honey – 2 tablespoons
• fresh thyme leaves – 1 teaspoon
• flaky sea salt (such as Maldon) – a pinch

Instructions

1. Make the dough: Whisk together the flour, salt, and sugar in a large bowl. Add the cold butter cubes and use your fingertips to press and smear the butter into the flour until the mixture looks like rough, shaggy crumbs with some pea-sized butter pieces still visible — those chunks are what create flaky layers, so don't overwork it. Drizzle in ice water one tablespoon at a time, tossing with a fork, until the dough just comes together when you squeeze a handful. It will look shaggy, not smooth. Flatten into a disk, wrap in plastic, and refrigerate for at least 1 hour or up to 2 days.
2. Caramelize the onions: Melt the butter with the olive oil in a large, wide skillet over medium heat. Add the sliced onions and salt, and stir to coat. Cook, stirring every 5 minutes or so, for 40–50 minutes total. You're looking for deeply golden, jammy onions — not just softened and translucent. If the onions start to stick or scorch, add a splash of water and scrape up the browned bits. In the last 5 minutes, add the thyme, then pour in the wine and stir until the liquid evaporates. Season with black pepper, remove from heat, and let cool completely.
3. Preheat your oven to 400°F / 200°C (convection: 375°F / 190°C) with a rack in the lower third. Line a large baking sheet with parchment paper.
4. Roll out the dough: On a lightly floured surface, roll the chilled dough into a rough 13-inch circle about ⅛ inch thick — it doesn't need to be perfect; rustic edges are part of the charm. Transfer it to the prepared baking sheet by folding it loosely in half or quarters, then unfolding it. Scatter ¾ of the Gruyère evenly over the dough, leaving a 2-inch border all around — this cheese layer acts as a moisture barrier and keeps the crust crisp.
5. Assemble: Spoon the cooled caramelized onions over the cheese layer and spread gently. Scatter the remaining Gruyère over the top. Fold the bare border of dough up and over the edge of the filling, pleating as you go — press the folds gently so they hold. Refrigerate the assembled galette for 15 minutes to firm up the butter in the pastry; this helps it hold its shape and bake crispier.
6. Egg wash and bake: Whisk the egg and milk together and brush it evenly over the exposed dough border. Bake for 35–40 minutes, until the crust is a deep golden brown and the cheese is bubbly and spotty with color. If the center looks pale at 30 minutes, don't pull it early — a fully golden crust is what you're after.
7. Glaze and finish: While the galette is in its final 5 minutes of baking, warm the honey in a small saucepan over low heat with the thyme leaves until fragrant, about 1 minute. When the galette comes out of the oven, brush the warm honey-thyme glaze over the entire filling and inner crust edge. Sprinkle with flaky sea salt. Let cool for 10 minutes before slicing — this lets the filling settle and makes cleaner cuts.