Melt 2 tablespoons of butter in a large skillet over medium-low heat. Add the thinly sliced yellow onions and a few sprigs of fresh thyme. Stir occasionally for about 40 minutes until the onions turn a deep golden brown.

Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper, then spread the bacon slices. Bake for 15-20 minutes until crispy, turning halfway through.

In a small bowl, combine ½ cup of mayonnaise with 2 tablespoons of A1 Steak Sauce, stirring until smooth. Refrigerate the sauce.

In a large mixing bowl, combine 1 pound of ground beef with 1 teaspoon of celery seeds, 1 tablespoon of dried minced onion, 1 tablespoon of dried parsley, and a pinch of black pepper. Mix and shape into 12 patties.

Heat a skillet over high heat and add cooking oil. Place the beef patties in the skillet, cooking for about 3-4 minutes on each side until golden-brown.

During the last minute of cooking, place a slice of Gruyère cheese on top of each patty. Cover the skillet until the cheese melts.

Slice slider buns in half and lightly toast. Assemble by placing a beef patty topped with cheese on each bun, add sweet caramelized onions, bacon, arugula, and drizzle with sauce.

Arrange the sliders on a serving platter and serve warm.