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Vegan French Onion Soup

Vegan French Onion Soup — Crockpot Recipe

Rich, caramelized onions, a splash of red wine, and a bubbly vegan cheese toast on top — only this time I make it in the crockpot so dinner practically cooks itself. Sound irresistible? Good. Let’s do it.
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Prep Time 10 minutes
Cook Time 50 minutes
Total Time 1 hour
Servings: 4
Course: crockpot, Soup
Cuisine: American
Calories: 440
Ingredients Equipment Method Notes

Ingredients
  

  • 1½ lb about 680 g onions, peeled and sliced into half-moons
  • 2 tbsp olive oil
  • 2 tbsp vegan butter use a high-quality plant butter for richness
  • 1 tbsp agave nectar or maple syrup
  • 3 cloves garlic minced
  • ¼ cup dry red wine
  • 3 cups low-sodium vegetable broth
  • 4 sprigs fresh thyme or 1 tsp dried thyme
  • ½ tsp salt adjust to taste
  • ¼ tsp ground black pepper
  • 4 slices French bread thick-cut (for toasting)
  • 1 cup shredded vegan gruyere or your favorite meltable vegan cheese
  • Bold tip: choose a vegan cheese labeled “good melting” — not all plant cheeses melt well.

Equipment

  • Large skillet or heavy-bottomed pan (for caramelizing onions)
  • Crockpot / slow cooker (4–6 quart size works well)
  • Oven-proof bowls or crocks (for broiling the cheese)
  • Baking sheet (to toast bread under the broiler)
  • Immersion blender or countertop blender (optional, if you like a smoother soup)
  • Wooden spoon and sharp knife
  • FYI: You can caramelize onions right in the crockpot on high, but I prefer a skillet for speed and better browning.

Method
 

  1. Caramelize the onions (you get the flavor here)
  2. Heat 2 tbsp olive oil + 2 tbsp vegan butter in a large skillet over medium heat. Add the sliced onions and a pinch of salt. Stir every few minutes and let the onions soften, darken, and caramelize for about 20–25 minutes. Toward the end, stir in 1 tbsp agave and 3 cloves garlic, and cook for another 3 minutes until everything smells nutty and sweet.
  3. Why this matters: I always say caramelization creates the soup’s backbone — skip this and you miss the soul.
  4. Deglaze & transfer to crockpot
  5. Pour ¼ cup dry red wine into the skillet and use a wooden spoon to scrape up the brown bits stuck to the pan. Let the wine reduce for about 1 minute, then transfer the onions + wine into the crockpot. Add 3 cups vegetable broth, thyme, salt, and pepper. Stir to combine.
  6. Slow-cook for depth
  7. Cover and cook on HIGH for 50 minutes (you can do LOW for 1.5–2 hours if you prefer). The crockpot will meld flavors and soften everything further. If you caramelized well, this shorter crockpot time gives you concentrated flavor without overcooking.
  8. Toast the bread
  9. When the soup nears done, preheat the oven broiler to high. Brush the bread slices lightly with olive oil or vegan butter, place them on a baking sheet, and toast 5–8 minutes until golden, flipping halfway.
  10. Assemble and broil
  11. Ladle soup into oven-proof bowls, place a toasted bread slice on top of each bowl, and sprinkle ~¼ cup shredded vegan cheese over each slice (divide the 1 cup among the bowls). Put the bowls on a rimmed baking sheet and broil 2–4 minutes until the cheese bubbles and browns. Watch closely — broilers work fast.
  12. Bold reminder: Use oven mitts — the bowls get hot.
  13. Crockpot-only option (no skillet)
  14. Pressed for time or too lazy to heat a pan? You can slice the onions, toss them with oil, salt, and agave directly in the crockpot, and cook on HIGH for 2–3 hours or LOW for 4–6 hours until deeply brown. The flavor won’t be as concentrated as skillet-caramelized onions, but it will still be delicious.
  15. IMO, skillet caramelization gives the best payoff, but the crockpot-only route works in a pinch.

Notes

Nutrition & calorie estimate (approximate)

I did a friendly estimation so you know what you’re eating. Numbers vary by brand and exact portion, so treat this as a guide.
  • Total calories (whole pot): ~1,760 kcal
  • Calories per serving (1/4 pot): ~440 kcal
  • Estimated macronutrients per serving:
    • Fat: ~22 g
    • Carbohydrates: ~45 g
    • Fiber: ~4–5 g
    • Protein: ~8–12 g (depends on vegan cheese choice)
    • Cholesterol: 0 mg (100% plant-based)
Bold note: vegan butter and vegan cheese contribute most of the calories; swap to lighter options to reduce calories.