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White Horse Style French Onion Soup

While the exact, official written recipe used by the kitchen at the original White Horse Inn in Milford, New Hampshire has never been formally published, its legacy—especially the giant, hearty crock topped with their signature homemade sourdough—remains a fond memory in local food lore.
Former kitchen staff and patrons recall that what set the White Horse onion soup apart from standard bistro versions was a combination of slow, deep-roasted caramelized onions, a rich beef and sherry broth, and their thick-cut, house-baked sourdough bread floated on top under a massive blanket of melted cheese.
Here is a recreation recipe that captures the exact taste, rich broth, and structure of the iconic White Horse Inn version.
Prep Time20 minutes
Cook Time1 hour 30 minutes
Total Time1 hour 50 minutes
Servings: 4 to 6 crock portions

Ingredients

The Soup Base

  • 4–5 (about 3lb) large yellow onions sliced thin root-to-stem
  • 3 Tbsp unsalted butter
  • 1 Tbsp olive oil
  • ½ tsp granulated sugar (helps the caramelization)
  • 3 cloves garlic minced
  • 2 Tbsp all-purpose flour (for body)
  • ½ cup dry white wine or dry sherry (for deglazing)
  • 6 cups high-quality beef stock or a 50/50 mix of rich beef stock and chicken stock for depth
  • 2 sprigs fresh thyme
  • 1 bay leaf
  • Salt and freshly cracked black pepper to taste

The Topping

  • Thick slices sturdy sourdough bread toasted or broiled until dry and golden
  • 2 cups shredded Swiss, Gruyère, or Provolone cheese (or a mix for meltability and bite)
  • Fresh thyme leaves for garnish

Instructions

  • Slow-Caramelize the Onions (The Key Step):
    Melt the butter with the olive oil in a large, heavy-bottomed Dutch oven over medium-low heat. Add the sliced onions, stirring to coat. Cover and let them soften for 10 minutes.
    Remove the lid, stir in the sugar, and turn the heat to low.
    Cook for 45 to 55 minutes, stirring every few minutes, until the onions turn a deep, rich mahogany brown. Don't rush this step—this is where all the deep flavor comes from.
  • Build the Broth:
    Stir in the minced garlic and cook for 1 minute until fragrant. Sprinkle the flour over the onions and stir constantly for 2 minutes to cook out the raw flour taste.
  • Deglaze & Simmer:
    Pour in the sherry or white wine, scraping up all the golden, caramelized bits stuck to the bottom of the pot.
    Cook until the alcohol reduces by half (about 2 minutes).
    Pour in the beef broth, thyme sprigs, and bay leaf. Bring to a gentle boil, then turn the heat to low, cover, and simmer for 30 minutes.
  • Finish the Soup:
    Remove the bay leaf and thyme sprigs. Taste the broth and season with salt and plenty of freshly cracked black pepper.
  • Broil and Serve:
    Preheat your oven's broiler.
    Ladle the hot soup into oven-safe ceramic crocks placed on a baking sheet. Float a thick slice of toasted sourdough bread on top of each crock. Generously heap the shredded cheese over the bread, letting a bit spill over the sides of the rim.
    Broil 3–5 inches from the heat element for 3 to 5 minutes, until the cheese is melted, bubbling, and browned around the edges.
    Serve and enjoy!