For the chicken, evenly sprinkle the spices all over both sides of the chicken. Heat a large skillet to medium-high heat with a few pats of butter. When the butter melts and browns slightly, add the chicken. Sear for about 3 minutes on each side until the chicken is cooked through, then remove from the heat. Let the chicken rest 5 minutes before slicing and serving.
For the butternut, add the squash cubes to a skillet (fitted with a lid) with the stock. Cover the skillet with a lid and turn the heat to high. When the stock boils, let boil for 5 minutes then remove the lid and reduce the heat to medium. Continue to boil/simmer the squash until the stock has mostly reduced and the butternut squash is very tender. Mash the squash with a spoon and swirl in the butter. Taste, and add salt and pepper to your preference.
To serve, top a heap of butternut with a piece of sliced grilled chicken. Top THAT with a dollop of pesto, and a sprinkle of grated manchego and pepitas. Devour.