PREP: Cut veggies and chicken before starting to cook; the process goes quickly! Finely chop the onion and garlic, cut the chicken breast into small pieces, and chop the broccoli into small pieces. Set out the rest of the ingredients.
COOK: Heat olive oil in a large (nonstick) pot over high heat. Add onion and stir around for 1-2 minutes and then add in garlic and stir for 30 seconds. Add the chopped chicken, season with salt and pepper; cook until mostly cooked through, about 5 minutes. Add in all the frozen vegetables (no need to thaw) and finely chopped broccoli. Stir for 2-3 minutes or until veggies are thawed and chicken is cooked through. Broccoli should be crisp-tender. Transfer this entire mixture to a plate and cover with foil.
COOK CONT.: Return the pot to burner. Melt the butter, whisk in the flour and cook and stir for 1 minute. Gradually add in the stock, whisking constantly. Add in the milk and all the uncooked orzo. Add in the Italian seasoning.
FINISH COOKING: Bring mixture to a simmer, then lower the heat until it is just barely and gently bubbling. Cook for 7 minutes without a lid, stirring occasionally and making sure to scrape the bottom so the orzo does not stick. After 7 minutes the pasta should be almost tender (mixture will still be soupy). Add the plate of veggies and chicken to the pot and stir. Add 3/4 cup Parmesan and stir to melt. Season to taste with salt and pepper. Don't be afraid to add a bit more-- the salt and pepper really pull all the flavors together.
SERVE: Consistency should be similar to risotto and very creamy. (Add a splash of milk if needed to thin consistency a bit.) Serve with additional 1/4 cup Parmesan if desired and some freshly chopped parsley. Enjoy while hot.