Cut the chicken breast into bite-sized pieces and finely chop the onion and garlic.
Heat the olive oil in a large pot over medium-high heat and sear the chicken until golden brown.
Add the onion and garlic to the pot, sautéing until the onion is translucent and fragrant.
Stir in the dry orzo pasta and toast for one minute to enhance the nutty flavor.
Pour in the chicken broth, dried oregano, sea salt, and black pepper, then bring to a boil.
Reduce heat to low, cover, and simmer for 8 minutes.
Place the broccoli florets on top of the orzo, cover again, and steam for 5 minutes until tender.
Remove from heat, stir in the juice and zest of the lemon, and fold in the parmesan cheese.