01 -
Heat a skillet over medium heat and add olive oil. Once hot, add the sliced onions, salt, and pepper. Cook for about 15 minutes, stirring occasionally, until onions become caramelized and golden brown.
02 -
Stir in garlic powder, dried thyme, and balsamic vinegar. Remove from heat and allow the mixture to cool for several minutes.
03 -
Lay the flank steak slices flat on a clean work surface.
04 -
Spread a thin, even layer of caramelized onion mixture over each steak slice. Sprinkle with shredded Gruyère cheese and chopped fresh parsley.
05 -
Roll up each steak slice from one end to form a tight pinwheel. Secure the ends with toothpicks or kitchen twine to hold the shape.
06 -
Preheat grill or grill pan over medium-high heat.
07 -
Place the pinwheels on the preheated grill and cook for 4 to 5 minutes per side, or until the steak reaches desired doneness.
08 -
Remove pinwheels from the grill and rest for several minutes. Carefully remove toothpicks or kitchen twine before slicing the pinwheels into bite-sized portions. Serve warm.