Step 1: Preheat oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.
Step 2: In a large skillet, heat olive oil over medium-high heat. Add chicken cubes and cook until browned and cooked through, about 8-10 minutes. Remove chicken and set aside.
Step 3: In the same skillet, add onion and garlic, cooking until softened, about 5 minutes.
Step 4: Add spinach to the skillet and cook until wilted, about 2-3 minutes.
Step 5: Reduce heat to low. Add cream cheese and chicken broth, stirring until cream cheese is melted and sauce is smooth.
Step 6: Stir in Parmesan cheese, thyme, salt, and pepper. Return chicken to the skillet and mix well.
Step 7: Transfer mixture to the prepared baking dish. Top evenly with shredded mozzarella cheese.
Step 8: Bake for 20-25 minutes, until cheese is melted and bubbly and edges are golden brown.
Step 9: Let cool for 5 minutes before serving.