Bring a large pot of salted water to a boil. Add the fusilli pasta and cook according to package instructions until al dente, usually about 8-10 minutes.

Once cooked, reserve 1 cup of pasta water, then drain the pasta in a colander and set aside.

In a large skillet, heat the olive oil over medium-high heat. Season the chicken pieces with salt and pepper.

Add the chicken to the skillet and cook for about 6-8 minutes, stirring occasionally, until the chicken is golden brown and cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, reduce the heat to medium and add the butter. Once melted, add the minced garlic and sauté for about 1 minute until fragrant, being careful not to burn it.

Pour in the heavy cream and stir well, bringing it to a gentle simmer. Allow it to cook for about 2-3 minutes to thicken slightly.

Stir in the grated Asiago cheese, spinach, cherry tomatoes, Italian seasoning, and red pepper flakes (if using). Mix until the cheese is melted and the spinach is wilted.

Add the cooked chicken back into the skillet and stir to combine. If the sauce is too thick, add reserved pasta water a little at a time until the desired consistency is reached.

Add the drained pasta to the skillet and toss everything together until the pasta is well coated with the sauce.

Serve hot, garnished with chopped parsley and additional Asiago cheese on top.