Peel the potatoes and shred on the large holes of a box grater. Place in a colander over a large bowl and toss with kosher salt. Set aside, allowing the potatoes to drain. \nMelt the butter in a small cast iron skillet or other 6-inch skillet over medium heat.\nPress down on the potatoes in the colander to remove some of the excess liquid and toss with cornstarch. \nSpread drained potatoes in an even, tightly-packed layer in the buttered skillet, pressing down firmly with a spatula. Continue cooking, undisturbed, until golden-brown and crispy on the bottom side, about 10 minutes. \nMeanwhile, in a small bowl, whisk together the heavy cream and Hong Kong sauce. Pour sauce mixture over the uncooked side of the potato pancake and sprinkle generously with salt. Carefully flip the potatoes (do not worry if they break a little during flipping). \nCook undisturbed on the other side until golden and crisp, about 8-10 minutes more. Transfer to a plate and sprinkle with chives and additional salt to taste. Slice into wedges and serve warm, topped with yogurt, sour cream or applesauce, if desired.