Lay chicken cubes on a double layer of paper towels, then top with a second double layer of towels. Press on top of paper towels to remove any excess moisture from the chicken.
In a 1-gallon resealable plastic bag, add all-purpose flour (1/2 cup), salt (1 teaspoon), black pepper (1/2 teaspoon), and Italian seasoning (2 teaspoons). Seal the bag and shake until evenly combined.
In batches, add the chicken and shake until all pieces are coated. Remove coated pieces to a plate. Repeat until all chicken is coated.
Add (2 tablespoons) olive oil and butter (2 tablespoons) to a high-sided 12-inch skillet. Over medium heat, brown chicken in batches (likely 3 batches in total), flipping over two or three times, until golden brown and the chicken reaches 165ºF (74ºC) when measured by an instant-read thermometer. Transfer cooked chicken to a plate.
Add remaining (1 tablespoon) olive oil to skillet and sauté garlic (1 tablespoon), shallots, and sun-dried tomatoes (1/2 cup). Sauté, over medium heat, for three minutes, stirring constantly, until softened and fragrant, about 3-5 minutes.
Keep the heat on. Add tomato paste (1/4 cup) and broth (1 cup) to skillet. Use a large wooden spoon to mix them together and scrape up all the brown bits on the bottom of the skillet.
Add the frozen tortellini (19 ounces), heavy cream, and parmesan (1 cup). Bring to a simmer (don't boil). Adjust heat, as needed, to maintain a low simmer. Simmer, stirring often, scraping the bottom of the pan with a wooden spoon so the Parmesan doesn't burn. Simmer until the tortellini is cooked, about 3-4 minutes.
To the skillet, add cooked chicken and spinach (2 cups), gently tossing until everything is well coated and combined. Spoon into individual serving bowls and top each with an indulgent sprinkle of Parmesan, a generous pinch of fresh basil, and fresh cracked pepper! Enjoy!!