The “sauce” is similar, I suppose, to a salsa verde (Italian, not Mexican), except it has nuts. And no capers or lemon. Anyway, the bright herbaceousness and the nutty flavors work really well with the earthy sweetness of the squash. Kabocha tend to be drier than other squash, such as acorn or butternut, so the topping is stands out all the more. Pine nuts are a great choice in lieu of hazels, and you could even give this dish a South West slant by using cinnamon and coriander seed on the squash and adding a little cilantro to the garnish. The peel is edible on kabocha by the way.