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image of the finished French onion crostini on a platter.

French Onion Soup Crostini

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These French Onion Soup Crostini are bite-sized perfection—caramelized onions, a touch of red wine, and gooey truffle Gouda on crisp crostini. Perfect for parties, appetizer spreads, or an indulgent snack, they bring all the rich, savory flavor of classic French onion soup into a fun, handheld version.

  • Total Time: 50 minutes
  • Yield: 12 crostini 1x

Ingredients

Units Scale
  • 12 crostini [see notes for dietary substitutions]
  • 1/4 lb Truffle Gouda, cut into 12 slices [see notes for substitutions]
  • 1 large or 2 small white onions, halved and thinly sliced [see notes for substitutions]
  • 2 Tbsp unsalted butter [see notes for dietary substitutions]
  • 1/2 cup beef broth [see notes for dietary substitutions]
  • 1/2 cup dry red wine (or extra broth) [see notes for substitutions]
  • 1/2 Tbsp flour [see notes for dietary substitutions]
  • 1/2 tsp brown sugar [see notes for substitutions]
  • 1/2 tsp Worcestershire sauce
  • 1/2 tsp Herbs de Provence [see notes for substitutions]
  • 1/4 tsp salt

Instructions

  • Melt butter in a large skillet over medium heat. Add onions and cook for 5 minutes, stirring constantly. Reduce to medium-low and cook 10–15 minutes until golden brown, stirring occasionally.

  • Add brown sugar and red wine. Cook, stirring, until wine evaporates and onions look deep and glossy (~10–15 minutes).

  • Stir in flour, Herbs de Provence, and salt until onions are fully coated.

  • Slowly add broth, stirring continuously. Add Worcestershire sauce. Bring to a boil over medium-high, then reduce to medium and cook 7–8 minutes, until most liquid evaporates.

  • Arrange crostini on a baking sheet. Top with onion mixture and Gouda slices. Bake at 350°F for 6–8 minutes, until cheese is melted and bubbly.

Equipment

Notes

Substitutions:

  • Onions: White onions cook faster, but yellow onions can also be used (1:1 ratio).
  • Red wine: Can be replaced with extra broth for alcohol-free version (1:1 ratio).
  • Cheese: Truffle Gouda can be substituted with plain Gouda(1:1 ratio).
  • Brown sugar: White sugar works in a pinch (1:1 ratio).
  • Herbs de Provence: Can substitute 1:1 with dried thyme.

Dietary Details and Substitutions

To make it Vegetarian:

  • Broth: Beef broth can be replaced with vegetable broth to make this fully vegetarian.

to make it Vegan:

  • Cheese: Truffle Gouda can be substituted with a vegan mozzarella (1:1 ratio).
  • Broth: Beef broth can be replaced with vegetable broth, in a 1:1 ratio,to make this fully vegetarian.

to make it Gluten free:

  • All-Purpose Flour: Use cornstarch or tapioca starch instead of flour (1:1 ratio)
  • Crostini: Use a Gluten free baguette to make the crostini instead of a traditional baguette.
  • Author: Jenn Giam Smith
  • Prep Time: 15 minutes
  • Cook Time: 35 minutes
  • Category: Appetizer/hor d'oerves
  • Method: Stove + Oven
  • Cuisine: French

Find it online: https://www.jenn-smith.com/french-onion-soup-crostini/