How to Make It
In a small skillet, heat 1/4 cup of the olive oil. Add the sage leaves and fry over high heat until deep green and translucent, about 1 minute. Transfer to a paper towellined plate to cool. Season with salt and pepper.
Bring a medium saucepan of salted water to a boil. Fill a large bowl with ice water. Blanch the brussels sprout leaves in the boiling water until tender, about 2 minutes. Using a slotted spoon, transfer the leaves to the ice water to cool. Drain and pat dry.
Heat the remaining 2 tablespoons of olive oil in a large, deep skillet. Add the squash and cook over moderate heat, stirring occasionally, until lightly browned in spots, about 8 minutes. Add the butter and continue cooking until the squash is tender, about 7 minutes longer. Add the brussels sprout leaves, season with salt and pepper and cook until heated through, about 3 minutes. Transfer to a bowl, scatter the fried sage and chives on top and serve.