Heat olive oil in a large skillet or Dutch oven over medium-high heat.
Season chicken cubes with salt and pepper, then sear in the skillet until browned and cooked through, approximately 6-8 minutes. Remove chicken and set aside.
In the same skillet, add minced garlic and sauté for 30 seconds until fragrant.
Add the dried orzo to the skillet and toast for 2 minutes, stirring frequently to prevent sticking.
Pour in the chicken broth and bring to a simmer. Reduce heat to medium-low, cover, and cook for 8-10 minutes, or until orzo is tender and most liquid is absorbed.
Stir in the Boursin cheese until fully melted and incorporated into a smooth, creamy sauce.
Fold in the fresh baby spinach and stir until wilted from the residual heat.
Return the cooked chicken to the pan and stir in the lemon juice to brighten the flavors. Serve immediately.