Step 1: Heat 1 tablespoon of olive oil in a large skillet or Dutch oven over medium-high heat. Add the diced chicken breast, season with salt and pepper, and cook until golden brown and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.
Step 2: Reduce heat to medium. Add a drizzle more olive oil if needed, then add the minced garlic and chopped sun-dried tomatoes to the same skillet. Sauté for 1-2 minutes until fragrant.
Step 3: Pour in the chicken broth, bringing it to a simmer and scraping up any browned bits from the bottom of the pan. Let it simmer for 2-3 minutes to slightly reduce.
Step 4: Stir in the heavy cream and 1/2 cup of grated Parmesan cheese. Continue to simmer, stirring frequently, until the sauce begins to thicken slightly, about 3-5 minutes. Season the sauce with salt, pepper, and red pepper flakes (if using).
Step 5: While the sauce is simmering, cook the fresh tortellini according to package directions in a separate pot of salted boiling water. Drain well once cooked.
Step 6: Add the cooked tortellini, cooked chicken, and fresh spinach to the skillet with the creamy sauce. Toss gently until the spinach has wilted and the tortellini is fully coated in the sauce. If the sauce is too thick, add a splash of reserved pasta water.
Step 7: Taste and adjust seasonings as needed. Serve immediately, garnished with additional Parmesan cheese and fresh herbs, if desired.