In a large pot, bring salted water to a boil. Add the orzo and cook according to package instructions until al dente. Drain and set aside.
In the same pot, heat the olive oil over medium heat. Add the onion and sauté until translucent, about 3-4 minutes. Stir in the minced garlic and cook for an additional 1 minute until fragrant.
Add the broccoli florets and cook for 2-3 minutes until they begin to soften.
Pour in the vegetable broth and allow it to come to a gentle boil. Reduce the heat to low and let it simmer for about 5 minutes until the broccoli is tender.
Stir in the cooked orzo, heavy cream, cheddar cheese, and Parmesan cheese into the pot. Mix until the cheese is melted and the sauce is creamy.
Add salt, pepper, and crushed red pepper flakes (if using) to taste. Stir until everything is well combined and heated through.
Remove from heat and let it sit for a couple of minutes to thicken slightly. Serve warm, garnished with freshly chopped parsley.