This is a 10" immature fruit of a Korean variety of winter squash. Korean people call it "young pumpkin." The two or three varities that produce similar fruit all have huge mature squashes, so I think they are varieties of Cucurbita maxima. In Los Angeles, the squashes continue to mature into November. The "young pumpkin" is much relished in Korean cuisine. It tastes slightly sweet and has a texture like zucchini.