• Start by slicing and chopping a red onion. Cut half of the red onion into rings, and set aside.
• Chop the other half of the red onion into a fine dice. Reserve half the diced red onion to use for the mushroom topping and reserve the other half of the diced onion to make the beef patties.

Make the beef patties:

• In a mixing bowl combine ground beef, ½ cup diced red onion, Worcestershire sauce, 2 cloves minced garlic, salt and pepper.
• Form meat into four equal sized thin patties the are a little larger than the Ciabatta rolls. The beef will shrink in size as it cooks on the grill.

Make garlic aioli:

• In a small bowl stir together mayonnaise 4 cloves minced garlic, salt and pepper to make a quick garlic aioli. Set aside.

For the mushrooms:

• Heat butter and olive oil in a large skillet over medium heat.
• Add sliced mushrooms and stir to coat them with the olive oil and butter.
• Cook them until they release their liquid, about 4-5 minutes.
• Add ½ cup diced red onions to the pan.
• Cook until onions are soft and all the liquid in the pan has cooked off.
• Add 2 cloves minced garlic and cook until fragrant, about 1 minute.
• Stir in the thyme, salt and pepper.
• Remove from heat and keep warm.

Cook beef patties:

• Grill beef patties on a barbecue grill over medium high heat for 6 minutes with the lid closed. Flip and cook on the second side for an additional 6 minutes.
• Top each patty with a slice of Provolone cheese and continue to cook the patties until the cheese melts, about 2-3 minutes.
• Toast both halves of the Ciabatta buns on the grill while the cheese melts onto the beef patties.

Assemble burgers:

• Spread the garlic aioli evenly onto both halves of the toasted Ciabatta buns.
• Place a handful of arugula on the bottom bun, top with red onion slices.
• Place burger patties on top.
• Divide sautéed mushrooms onto each beef patty.
• Top with second Ciabatta bun.
• Serve warm and melty.