Cut the chicken breast into bite-sized pieces and season with half of the sea salt, black pepper, and dried thyme.
Heat the olive oil in a medium skillet over medium-high heat. Add the chicken and sear until golden brown on all sides, then remove and set aside.
In the same skillet, add the diced yellow onion and cook for 3 minutes until translucent. Stir in the minced garlic and cook for another 30 seconds until fragrant.
Add the dry orzo to the skillet and toast for 1 minute, stirring constantly to prevent burning.
Pour in the chicken broth and the remaining seasonings. Bring to a simmer, then reduce heat to low, cover, and cook for 8-10 minutes until the orzo is tender and most liquid is absorbed.
Stir in the heavy cream and fresh baby spinach, folding until the spinach is wilted and the sauce is creamy.
Add the cooked chicken back into the skillet, toss to combine and heat through, then serve immediately.