**Sauté Onion and Garlic:** Heat olive oil or butter in a large skillet over medium heat. Add the onion and cook until softened, about 3 minutes. Stir in the garlic and cook for 1 minute more.
**Toast the Orzo:** Add the orzo pasta to the skillet and stir to coat in the oil. Cook for 2-3 minutes, stirring occasionally, until lightly toasted.
**Add Broth and Cook Orzo:** Pour in the chicken or vegetable broth. Bring to a boil, then reduce the heat to low. Cover and simmer for 8-10 minutes, stirring occasionally, until the orzo is tender and most of the liquid is absorbed.
**Add Broccoli:** Stir in the chopped broccoli, cover, and cook for another 3-4 minutes, until the broccoli is tender and bright green.
**Make It Cheesy:** Reduce the heat to low. Stir in the milk or heavy cream, shredded cheddar cheese, and Parmesan cheese. Mix until the cheese is fully melted and the dish is creamy.
**Season and Serve:** Season with salt, pepper, and red pepper flakes (if using). Serve warm.