Pat the steak bites dry and season with salt and pepper. Let them rest at room temperature while you caramelize the onions.
Place a large skillet over medium-low heat and add 1 tablespoon butter and 1 tablespoon olive oil. Once hot, add the sliced onions. Cook, stirring occasionally, for 30-40 minutes, until the onions are soft and deeply golden brown. (Add a splash of water if they start to stick or brown too quickly.)
Stir in the garlic and cook for 1 minute. Transfer the onion mixture to a bowl and set aside.
Return the skillet to medium-high heat. Add the remaining butter and oil. Once butter has melted and the oil is hot and shimmering, add steak bites in a single layer (working in batches if needed) and sear for 1 ½ to 2 minutes without moving. Flip and cook for another 1 to 2 minutes, or until the steak reaches your desired doneness*. Transfer the steak bites to a plate, tent loosely with foil, and let rest while you finish the orzo.
Reduce the heat to medium. In the same skillet (do not wipe it out), add the orzo to the pan and stir to coat, scraping up the browned bits as you go.
Pour in the beef broth and Worcestershire sauce, stirring to combine.
Reduce heat to medium-low and bring the mixture to a simmer. Cover and cook for 8-10 minutes, stirring occasionally to prevent sticking, until the orzo is tender and most of the liquid has been absorbed.
Stir the caramelized onion mixture back into the skillet. Add Parmesan and mix until creamy and smooth.
Serve steak bites over creamy caramelized onion orzo.
Garnish with chopped parsley and extra Parmesan, if desired.