French Onion Soup Turned Into a Smashburger

Welcome to my new series, where I take smashburgers 🍔 way beyond the ordinary. Each episode, I’m stacking bold flavors, crazy twists, and over-the-top ideas to create burgers you’ve never seen before. Next, we’re making the French Onion Smashburger. This is a gourmet twist that brings all the cozy, cheesy richness of French onion soup to a burger with a delicious beefy au jus for dipping. Enjoy!! 😋

🧅 French Onion Smashburger
Ingredients (makes 2 burgers)

For the onions:
2 large yellow onions, thinly sliced
2 tbs butter
1 tbs avocado oil
1/2 tsp salt
1/2 tsp sugar
1/4 cup beef stock (or more as needed)
1 tsp fresh thyme (or ½ tsp dried)
Dash of Worcestershire sauce

For the smashburgers:
8 oz ground beef (80/20 blend works best)
Salt & pepper
sliced Gruyère cheese

For the buns:
2 brioche buns
2 tbs of Kerrygold garlic and herb butter, melted

Instructions
1. Caramelize the Onions
Heat butter + oil in a skillet over medium-low heat.
Add sliced onions, sprinkle with salt (and sugar if using). Cook low and slow, stirring often.
After about 20 minutes, deglaze with a splash of beef stock, add thyme + Worcestershire.
Continue cooking until onions are deep golden brown (30–40 minutes total).

2. Smash the Burgers
Form ground beef into 2 loose balls.
Heat Blackstone griddle until smoking hot.
Place a ball down, season with salt, and pepper.
Smash flat with a burger press.
Cook 2–3 minutes until a crust forms, flip, and immediately top with Gruyère cheese. Cover for 1-2 mins with a lid until cheese melts.

3. Garlic Butter Buns
Melt garlic and herb butter.
Brush on buns and toast cut side down until golden brown.

4. Build the Burger
Bottom bun → layer of caramelized onions
Smashburger patty with melted Gruyère
More caramelized onions piled high
Top bun brushed with garlic butter
Serve hot, gooey, and dripping with flavor

🥩 Beef Au Jus for Dipping
Ingredients (makes about 1 cup)
2 cups beef stock
1 tbs Worcestershire sauce
1/2 small onion, finely chopped
2 garlic cloves, smashed
1 sprig fresh thyme (or ½ tsp dried thyme)
1 bay leaf
1/2 tsp black pepper
1 tbs butter

Instructions
In a saucepan, melt butter over medium heat.
Add onion and garlic, sauté until lightly golden and fragrant (3–4 minutes).
Deglaze & simmer
Pour in beef stock and Worcestershire sauce.
Add thyme, bay leaf, and black pepper.
Simmer for 10–15 minutes to let flavors combine.

Strain & serve
Strain through a fine mesh sieve to remove solids.
Serve hot in small ramekins alongside your burger for dipping.

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