📝 About This Recipe
Indulge in the deep, soul-warming flavors of a Parisian bistro without the carb-heavy consequences. This keto-friendly rendition features yellow onions slow-caramelized to a rich mahogany, deglazed with dry white wine, and simmered in a robust beef bone broth. Topped with a savory, grain-free almond flour crouton and a bubbling blanket of melted Gruyère, it delivers all the luxurious texture and sweetness of the original classic.
🥗 Ingredients
The Soup Base
- 5 large Yellow Onions (thinly sliced pole-to-pole)
- 4 tablespoons Unsalted Butter (high-quality grass-fed preferred)
- 1 tablespoon Olive Oil (to prevent butter from burning)
- 6 cups Beef Bone Broth (rich and dark)
- 1/2 cup Dry White Wine (such as Sauvignon Blanc or Pinot Grigio)
- 4 sprigs Fresh Thyme (tied with kitchen twine)
- 1 piece Bay Leaf (dried)
- 2 cloves Garlic (minced)
- 1 teaspoon Sherry Vinegar (to balance the sweetness)
- to taste Salt and Black Pepper (kosher salt and freshly cracked)
Keto Croutons
- 1 1/2 cups Almond Flour (super-fine, blanched)
- 1 teaspoon Baking Powder
- 2 large Eggs (beaten)
- 3 tablespoons Melted Butter (slightly cooled)
- 1/2 teaspoon Garlic Powder
The Gratin
- 1 1/2 cups Gruyère Cheese (freshly shredded)
- 1/4 cup Parmesan Cheese (finely grated for extra crust)
👨🍳 Instructions
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1
In a large heavy-bottomed Dutch oven, melt the 4 tablespoons of butter with the olive oil over medium-low heat.
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2
Add the sliced onions and a pinch of salt. Cook slowly, stirring every 5-10 minutes. The key is patience; let them turn a deep, jammy caramel brown. This should take 45-50 minutes.
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3
While onions caramelize, prepare the croutons. In a bowl, whisk almond flour, baking powder, garlic powder, eggs, and melted butter until a thick batter forms.
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4
Spread the batter into a greased small rectangular microwave-safe dish (or bake at 350°F for 12 minutes). Microwave for 90-120 seconds until set. Let cool, then slice into rounds or squares that fit your soup crocks.
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5
Toast the keto bread slices in a pan with a little butter until golden and crisp on both sides. Set aside.
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6
Once onions are dark mahogany, add the minced garlic and cook for 1 minute until fragrant.
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7
Pour in the white wine to deglaze the pot, scraping up all the brown bits (fond) from the bottom with a wooden spoon.
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8
Add the beef bone broth, thyme sprigs, and bay leaf. Bring to a simmer, then reduce heat to low and cook for 20 minutes to marry the flavors.
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9
Remove the thyme sprigs and bay leaf. Stir in the sherry vinegar and season with salt and pepper to taste.
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10
Preheat your broiler. Arrange four oven-safe soup crocks on a sturdy baking sheet.
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11
Ladle the hot soup into the crocks, leaving about an inch of space at the top.
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12
Place a keto crouton on top of each bowl, then pile generously with the shredded Gruyère and Parmesan mix.
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13
Place under the broiler for 3-5 minutes, or until the cheese is bubbling and boasts golden-brown toasted spots. Watch carefully to avoid burning!
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14
Let the crocks sit for 2-3 minutes before serving, as the ceramic and the soup will be incredibly hot.
💡 Chef's Tips
Don't rush the onions; the deep flavor comes from the slow breakdown of sugars, so keep the heat low to avoid bitter charred edges. If the onions look too dry during caramelization, add a tablespoon of water or broth to help them soften. Use a high-quality Gruyère; pre-shredded cheese often contains potato starch as an anti-caking agent, which adds unnecessary carbs. For an even deeper flavor, use a mixture of beef and chicken stock (50/50 ratio). If you don't have sherry vinegar, a splash of balsamic vinegar works, though it has slightly more sugar.
🍽️ Serving Suggestions
Serve with a crisp green salad tossed in a simple lemon-dijon vinaigrette to cut through the richness. Pair with a chilled glass of the same dry white wine used in the recipe. A side of roasted marrow bones makes this an ultra-luxurious keto feast. For a non-alcoholic substitute, use a tablespoon of apple cider vinegar in place of the white wine deglaze. Finish with a sprinkle of fresh chives for a pop of color and mild onion bite.