Pat the chicken cutlets dry and season both sides with half the salt, half the pepper, and the garlic powder.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the chicken and sear for 4 to 5 minutes per side without moving, until golden brown and cooked through to an internal temperature of 165°F (74°C). Remove to a plate and tent loosely with foil.
Reduce the heat to medium and add the butter to the same skillet.
Add the minced garlic and cook for 1 minute, stirring, until fragrant and just beginning to turn golden.
Pour in the white wine and scrape up any browned bits from the bottom of the skillet. Let it simmer for 2 minutes until reduced by half.
Add the chicken broth, heavy cream, Italian seasoning, remaining salt, remaining pepper, and red pepper flakes if using. Stir to combine.
Simmer the sauce over medium heat for 5 to 6 minutes, stirring occasionally, until it has reduced and thickened enough to coat the back of a spoon.
Add the fresh spinach to the skillet and stir for 1 to 2 minutes until fully wilted into the sauce.
Stir in the Parmesan and taste the sauce, adjusting seasoning as needed.
Return the seared chicken to the skillet, spoon the sauce and spinach over the top, and simmer for 1 to 2 minutes to heat the chicken through.
Serve directly from the skillet with extra Parmesan if desired.