Cook your pasta according to the directions on the package for al dente - make sure your pasta water is salted. Reserve 1 cup of pasta water before draining pasta. Set both aside.
Slice your chicken into very thin bite sized pieces. Set aside *For an idea of size, look at the image in the post, you want the chicken thin.
In a large pan, heat up the olive oil and butter over medium heat until melted and slightly frothy. Add in the onions and cook until translucent, about 5 minutes. Next, add in the mushrooms and garlic and saute until the mushrooms are wilted, another 3-5 minutes.
To the pan, add in the curry paste and mix well until it's slightly melted and incorporated with the vegetables. Once combined, add in the cream, maple syrup, ½ cup of reserved pasta water and thinly sliced chicken breasts.
Simmer the sauce over medium heat for 5 minutes. Add in the spinach and contine to simmer over medium heat until the chicken is cooked to 165 degrees C and the sauce is thickened to your liking.
Taste the sauce for seasoning and add the rest of your reserved pasta water to the sauce to thicken as needed. You will need more/less depending on your preferred sauce thickness.
Once the sauce is done, add the cooked penne noodles into the pot and stir to combine.
Serve with a side salad and garlic bread and optionally topped with parsley.