French Onion Baked Brie

Published: Dec. 22, 2025

Overview

An elegant, crowd-pleasing appetizer featuring creamy, melted Brie topped with sweet caramelized onions, served with crisp baguette crostini and fresh accompaniments. Total preparation time: 45 minutes (5 minutes prep, 40 minutes cook).

Ingredients

Caramelized Onions

  • 2 tablespoons extra-virgin olive oil

  • 1 large Spanish onion, halved and thinly sliced (about 4 cups)

  • 2 fresh thyme sprigs or 1 rosemary sprig

  • ½ teaspoon balsamic vinegar

  • ¼ teaspoon salt (to start) + additional salt to taste

Crostini

  • 1 small baguette (8 ounces), sliced on the bias into ½-inch thick pieces

  • 1–2 tablespoons extra-virgin olive oil (for brushing)

Brie

  • 8 ounces Brie cheese (rind left on)

For Serving

  • Chopped fresh herbs (dill, parsley, mint, or chives)

  • Grapes, tangerine segments, or toasted nuts (optional)

Preparation

  1. Preheat Oven

Set oven to 350°F (175°C).

  1. Caramelize the Onions

  2. In a medium skillet, heat olive oil over medium-low heat. Add sliced onions, thyme/rosemary, and a pinch of salt.

  3. Cook slowly, stirring occasionally, until deeply browned and jammy (edges caramelized, center tender), 20–30 minutes. If the pan dries, add 1–2 tablespoons water.

  4. Stir in balsamic vinegar; adjust salt to taste. Cool completely before using. Note: Onions can be made 3 days ahead and refrigerated.

  5. Make Crostini

  6. Brush one side of each baguette slice with olive oil. Arrange oiled-side-up on a rimmed baking sheet.

  7. Bake until golden and crisp, 8–13 minutes (check after 8 minutes). Note: Crostini can be made 4 hours ahead or while the cheese bakes.

  8. Bake the Brie

  9. Remove Brie from the fridge (cold) and place in a ceramic gratin dish or glass baking dish.

  10. Top with cooled caramelized onions.

  11. Bake on a lower rack (below crostini rack if baking simultaneously) until cheese is soft and oozing, 9–15 minutes.

  12. Serve

  13. Sprinkle with fresh herbs. Pair with crostini and optional accompaniments (grapes, tangerine, nuts).

Serving Tips

  • Add toasted walnuts or dried cranberries (sautéed with onions) for extra texture.

  • Drizzle with honey or fig jam for a sweet contrast.

Review Highlights

  • “Made for Christmas Eve—jammy onions + melted Brie = elegant simplicity. Served with dried fruit and honey.”

  • “Years of success with dried cranberries in the onions—always a hit!”

  • “Works with vegan cheese! A hit with dairy-allergy family members.”

Adapted from Melissa Clark’s recipe; notes from user reviews.