Wagyu French Onion Sliders Recipe

Prepare onions

Peel and thinly slice onions into half-moons. Measure ~2 cups sliced (about 2 medium onions).

Heat a large heavy skillet over medium-low heat. Add butter and olive oil and let butter melt and foam but not brown.

Add sliced onions, 1 tsp salt, and 1 tsp sugar to the pan. Stir to coat and spread onions evenly across the pan so they make good contact.

Cook slowly over medium-low heat, stirring every 4–6 minutes. After 15–20 minutes the onions will soften and begin to turn golden at the edges. Continue cooking a total of 30–40 minutes until deep golden-brown and jammy; lower heat if they start to darken too fast.

When onions are deeply browned, deglaze the pan with 2 tbsp dry red wine or sherry (if using), scraping up browned bits. Cook until liquid is absorbed. Remove from heat and set aside.

Place 1 lb ground wagyu in a bowl. Add 1 tsp salt, 1 tsp freshly ground pepper, and 1 tbsp Worcestershire sauce. Gently fold to combine; avoid overworking to keep patties tender.

Divide the mixture into 12 equal portions (about 1.3 oz / 37 g each) for small sliders. Shape each portion into a loose, thin patty slightly wider than the buns, about 1/4" thick; make a slight thumb indentation in the center of each patty to minimize doming while cooking.

Preheat a large cast-iron skillet or griddle over medium-high heat until hot. If desired, brush with a little neutral oil and wipe excess so you get a good sear without smoke.

Cook patties in batches (do not overcrowd). Sear 1–2 minutes per side for medium-rare to medium, until a brown crust forms; flip only once. If patties are very thin, total cook time may be 2–3 minutes. Remove to a plate and tent loosely with foil. Reserve drippings in pan for flavor.

Preheat oven to 375°F (190°C) if you prefer to melt cheese on multiple sliders at once, or use the same skillet for finishing.

Split the 12 mini brioche buns. Lightly brush cut sides with 2 tbsp melted butter and arrange cut-side up on a baking sheet. Toast in oven 4–6 minutes until lightly golden, or toast buttered buns in a skillet over medium heat until golden.

If using an oven, arrange bottom buns on the baking sheet. Spread ~1/2 tsp Dijon mustard on each bottom bun and a thin layer (~1/4 tsp) mayonnaise if desired.

Place a wagyu patty on each bottom bun. Top each patty with a generous spoonful (~2 tbsp) of warm caramelized onions, then pile or cover with ~1 tbsp (about 1 oz) Gruyère per slider.

Return to the oven for 2–3 minutes until cheese melts. Alternatively, place assembled sliders briefly under a broiler or cover skillet with a lid to melt cheese (watch closely to avoid burning).

Place toasted top buns over sliders, garnish with a few thyme leaves if using, and serve immediately.