Prepare the caramelized onions by slicing 2 large onions thinly
Heat 2 tbsp butter and 2 tbsp oil in a pan over medium heat
Add sliced onions, 2 tsp sugar, and 1 tsp salt
Cook until onions are caramelized and golden brown
Mix the sauce ingredients: 3 tbsp mayonnaise, 2 tbsp ketchup, 1 tsp siracha, 1 tsp mustard, 1 tsp pickle juice or vinegar, 1 tsp sugar, ¼ cup finely diced pickles, and salt & pepper to taste
Season 400g ground beef with salt, black pepper, 1 tsp garlic powder, and 1 tsp onion powder
Form small beef patties and smash them flat in a hot skillet
Cook until browned and crispy, then add cheddar cheese slices
Toast the large butter croissants with butter until golden
Assemble the burgers: spread sauce on croissant buns, add lettuce, tomato, cucumber, smashed beef patty with cheese, and caramelized onions
Serve immediately
