Heat butter or olive oil in a large skillet over medium heat.
Add diced onion and sauté until soft and fragrant, about 2-3 minutes.
Stir in the chicken sausage, breaking it up as it cooks, until browned.
Add minced garlic, sundried tomatoes, and tomato paste. Stir and cook for another minute until everything is coated and smells amazing.
Pour in the orzo and a pinch of salt, stirring to toast the pasta slightly.
Add the chicken broth, bring to a boil, then cover and cook for 10-12 minutes on very low heat, stirring occasionally, until the orzo is tender and has absorbed most of the liquid (but not all!) Stir in the fresh spinach until wilted.
Add in the the pecorino romano and stir until melty and creamy. Add in the soft cheese and splash of milk, if using. Remove from heat and enjoy!