Pat the chicken completely dry with paper towels. Cut the chicken into bite-sized cubes and season with salt and pepper as desired. Toss in 1 1/2 tablespoons of cornstarch until fully absorbed into the chicken.

Spritz a large nonstick skillet with cooking spray over medium-high heat. Add the chicken in two batches, allowing them to brown evenly. Cook each side for 2-3 minutes, until a light golden-brown crust forms.

Remove the chicken from the pan and let rest on a plate. Reduce the heat to medium.

Sauté the onions in the pan for about 3-4 minutes, or until slightly golden. Mix in the mushrooms and increase the heat to medium-high.

Let the mushrooms sit for a few minutes over the heat until slightly caramelized, then start mixing and sautéing until they become somewhat soft, about 5 minutes. Add the garlic and 1 teaspoon of salt, along with the optional red pepper flakes. Sauté for 1 more minute.

In a separate cup, whisk 1 tablespoon of cornstarch into the Madeira wine and half and half. Pour this mixture into the pan to deglaze. Reduce the heat to medium-low and simmer until thickened, about 5 minutes.

Add the chicken back to the pan and simmer in the sauce for another 3-5 minutes. Season with black pepper to taste. Taste the sauce and add an extra 1/2 teaspoon of salt if needed.

Mix the pasta and a few splashes of the reserved pasta cooking water into the sauce until everything is evenly coated. Continue to cook on low heat until the sauce has started to absorb into the pasta, about 2-3 minutes. Add more pasta water if the pasta gets too dry.

Mix in the grated Parmesan cheese until melted and serve.