Sprinkle the chicken with salt and pepper on both sides.: The moment you season the chicken you'll notice the salt drawing out a faint moisture, which helps the exterior brown more evenly during searing. You should smell a clean savory note from the seasoning, and the skin will start to dry slightly at the surface, which is what you want for crisping. A common mistake is underseasoning, which leaves the finished dish bland, or over salting early on if your pan is small, which can concentrate flavors too much. Be generous but measured, and pat the seasoning into the meat for even coverage.
Heat the oil in a large skillet over medium-high heat. Add the chicken and sear for about 2 minutes. Reduce the heat to medium, and keep frying the chicken until cooked through. The cooking time will vary, depending on the thickness of the chicken.: As the olive oil shimmers and the chicken hits the pan, you'll hear a satisfying sizzle that signals the Maillard reaction is starting. That sound changes to a steadier sizzling as the crust forms and the aroma becomes savory and slightly nutty. Visual cues are golden brown edges and clear juices; if the pan smokes heavily your heat is too high. A frequent error is crowding the pan, which causes steaming rather than searing, so give each piece space. Use a probe or cut into the thickest part to check doneness rather than guessing by time alone.
Remove the chicken from the skillet and set aside. To the same skillet, add the onions and cook for about 5 minutes, until soft and golden in color. Add the red pepper flakes and roasted peppers, and cook for another 2 minutes.: The pan will hold those browned bits from the chicken , which dissolve into flavor as you cook the onion . As the onion softens you will smell sweet, caramelized notes that mingle with the faint heat of the red pepper flakes. When you add the roasted peppers their smoky perfume lifts the mixture. A common pitfall is rushing the onion so it remains raw and sharp; patience here builds the backbone of the sauce. Stir regularly and use the spatula to scrape up fond, that's where concentrated flavor lives.
Reduce the heat to medium-low, add the cream, and bring to a simmer. Add the spinach, and when it wilts down, add the Parmesan. Stir the sauce.: When the Half & Half hits the warm pan you will see gentle steam and small bubbles as it approaches a simmer. Keep the heat moderate to prevent scalding, and watch the liquid thicken slightly as it reduces. Adding the spinach introduces a quick burst of green aroma and a soft hissing as it wilts; it will collapse dramatically, releasing a touch of moisture that blends into the sauce. Folding in the grated Parmesan cheese off heat or on very low heat helps it melt smoothly without clumping. Avoid boiling vigorously, which can separate the dairy and make the texture grainy.
Return the chicken to the skillet, and cook for 5 minutes, spooning the sauce over it. Remove the skillet from the heat. Garnish with freshly chopped parsley.: As you nestle the seared pieces back into the sauce, you'll notice the tempting aroma of browned meat mingling with creamy, cheesy notes. Spoon the sauce over each piece so the flavors penetrate and the surface rewarms gently. After about the suggested time the chicken should be fully cooked and glossy with sauce. Take it off the heat to avoid overcooking, which dries the meat and dulls the sauce. Finish with bright, chopped parsley to add a fresh herbal lift and a burst of color that contrasts beautifully with the creamy sauce.