Name: French Onion Soup Sourdough Bread
Prep time: 1860 min
Cook time: 45 min
Total time: 2025 min
Ingredients: 4 tablespoons unsalted butter; 2 large yellow onions (thinly sliced); 1 tablespoon Diamond Crystal Kosher Salt (use ½ tablespoon if using Morton's brand or table salt, or measure by weight); 4 cloves garlic (minced); 2 tablespoons thyme leaves (removed from stem); 1 ½ cups (360 grams) beef stock; ½ cup (100 grams) active sourdough starter; 4 cups (480 grams) bread flour; 1 teaspoon (3 grams) Diamond Crystal Kosher Salt (use ½ teaspoon if using Morton's brand or table salt, or measure by weight); 1 cup (100 grams) Gruyère cheese (shredded); Rice flour (for proofing basket); 2 ice cubes (for steam)

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This French Onion Soup Sourdough Bread is rich, soft, and deeply flavorful with sweet caramelized onions, melted Gruyère, and savory beef stock baked into every bite.

A whole loaf of French onion soup sourdough bread.

"The flavor is so intense and so good, I can’t get over how it tastes like French onion soup!"

My neighbor sent me that text after I shared a loaf of this French onion soup sourdough bread with her. She said made grilled cheese with it and it was the best she'd ever had.

This is easily one of the most flavor-packed sourdough inclusion loaves I’ve made so far. You’ve got two whole onions caramelized in butter, then simmered with garlic, thyme, and beef stock. Fold in freshly grated Gruyère and it really does taste just like a cozy bowl of soup baked into sourdough.

I tested this one a few times because all that richness does make for a slightly heavier dough, so you’ll notice a bit less oven spring than a classic loaf. But it’s honestly not enough to be a huge issue. And the flavor payoff more than makes up for it.

If you love French onion soup (or even just caramelized onions in general), this one is a must-try.

Hope you love it as much as I do!

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Ingredients & Substitutions

Here are some notes on key ingredients. For a full list of ingredients, check out the recipe card below.

Active Sourdough Starter- Use a bubbly, recently fed starter for the best rise. You can also use 1–2 day old discard, but fermentation may take slightly longer.
Onions- I use 2 large sweet yellow onions, thinly sliced into half-moons. Sweet onions work best here because they caramelize beautifully and give that classic French onion soup flavor.
Beef Stock- Use about 1 ½ cups of homemade or high-quality store-bought stock. Adjust slightly for your preferred hydration if needed.
Gruyère Cheese- Shred your own for best melt and flavor. Swiss or mozzarella + parmesan can be substituted.
Thyme & Garlic- Fresh is best, but dried thyme (about ⅓ the amount) can be used.
Bread Flour- Provides structure, chew, and height. All-purpose flour can be used but loaf may be slightly flatter and more dense.
Kosher Salt- Enhances flavor and strengthens the dough. I use Diamond Crystal Kosher Salt (2.8 grams per teaspoon). If using Morton’s or table salt, use about half as much by volume or weigh for accuracy.

The ingredients to make French onion soup sourdough bread. Each ingredient is labeled with text. They include bread flour, sourdough starter, onion, beef stock, garlic, thyme, Gruyere, butter, and salt.

Tips for Success

Weigh your ingredients. A kitchen scale gives the most accurate hydration and the most consistent results every time.
Use an active starter. Make sure your starter is bubbly and recently fed so the dough rises properly. You can use 1–2 day old discard, but fermentation may take longer.
Use fresh ingredients. Freshly shredded Gruyère, along with fresh thyme and garlic, makes a noticeable difference in flavor.
Watch the dough, not the clock. Bulk fermentation is complete when the dough looks puffy, airy, and roughly doubled. Timing will vary based on temperature and starter strength.
Expect a heavier dough. Because this dough includes butter, cheese, and moisture-rich caramelized onions, it won’t have as much oven spring as a classic sourdough. To help lighten it, you can drain or lightly pat the onions before adding the stock, or use only half of the caramelized onions in the dough.
Cool before slicing. Allow the bread to cool for at least 2 hours before slicing so the crumb can fully set and avoid a gummy texture.

How to Make French Onion Soup Sourdough Bread

Follow these step-by-step photos to make your own caramelized onion sourdough bread. Full details are in the recipe card below.

Step 1: Feed starter. Make sure it’s bubbly and active before mixing the dough.

An active sourdough starter in a glass mason jar.

Step 2: Make soup. Cook onions in butter with salt over medium-low heat until deeply golden (about 1 hour). Add garlic, thyme, then beef stock. Cool to 90°F or below.

Caramelized onions, garlic, and thyme in a stainless steel pot.

French onion soup in a stainless steel pot.

Step 3: Mix dough. Combine cooled soup with starter, flour, and salt. Mix until no dry flour remains. Rest 20 minutes.

French onion soup whisked together with active sourdough starter in a bowl.

French onion soup sourdough bread dough in a bowl.

Step 4: Stretch and fold. Add Gruyère during first set of stretch and folds (¼ each round). Complete 4 sets total, resting 15 minutes between each set.

Gruyere cheese being folded into sourdough bread dough.

Gruyere cheese being folded into the dough.

Stretched and folded French onion soup sourdough bread dough in a bowl.

Step 5: Bulk fermentation. Cover and let the dough rise until nearly doubled and bubbly, about 4–12 hours.

French onion soup sourdough bread dough in a straight-sided container before bulk fermentation.

French onion soup sourdough bread dough in a straight-sided container after bulk fermentation.

Step 6: Shape. Gently shape the dough into a tight round.

French onion soup sourdough bread dough being shaped on a floured counter.

French onion soup sourdough bread dough being shaped into a round ball on a floured counter.

Step 7: Proof.Transfer to a floured proofing basket, cover, and refrigerate overnight.

French onion soup sourdough bread dough in an oval proofing basket before cold proofing overnight.

French onion soup sourdough bread dough in an oval proofing basket after cold proofing overnight.

Step 8: Bake. Preheat oven to 450°F with a Dutch oven inside. Score the dough, add 2 ice cubes to the pot for steam, and bake 45 minutes covered, then 5 minutes uncovered. Let cool at least 2 hours before slicing.

French onion soup sourdough bread being scored on a piece of parchment paper.

A baked loaf of French onion soup sourdough bread on a wire cooling rack.

Baker's Timeline

Here’s a sample timeline to help you plan your French onion sourdough bread.

8:00 PM (Night Before): Feed your starter.
7:00-8:00 AM: Make French onion soup base.
8:00–8:30 AM: Mix the dough and let it rest for 20 minutes.
8:30–9:30 AM: Perform stretch and folds; add cheese.
9:30 AM–5:30 PM (varies): Bulk fermentation (until nearly doubled in size).
5:30–6:00 PM: Shape the dough.
6:00 PM–6:00 AM (Next Day): Cold proof in the fridge overnight.
6:00–6:45 AM: Bake at 450°F.
6:45–8:45 AM: Cool completely before slicing.

Note: Rise times can vary depending on the strength of your starter and the temperature of your kitchen. Always use visual cues—like a dough that has doubled and looks airy—rather than relying strictly on the clock.

How to Store

Store French onion soup sourdough bread (whole or sliced) in a bread box or airtight container at room temperature for up to 3 days.

For longer storage, slice the loaf and freeze it in a freezer-safe bag for up to 3 months. Thaw slices at room temperature or pop them straight into the toaster or oven to warm through.

A slice of French onion soup sourdough bread.

A cover of a recipe ebook with the title "Everyday Sourdough: 27 Sweet & Savory Sourdough Discard Recipes." There is an image of sourdough discard cinnamon rolls on the front. At the bottom, it reads "By Ashley Petrie of Everyday Homemade."

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