Place yams and sweet potatoes in a large saucepan, covering them with cold water by a few inches. Add a pinch of salt and bring to a boil. Reduce heat and simmer until potatoes are tender when pierced with a knife, about 10-15 minutes. Drain.

Meanwhile, heat peanut oil in a large skillet over medium heat. Add garlic, ginger and shallots and sauté until fragrant, about 3-4 minutes. Add choy sum leaves and cook until wilted, stirring occasionally, about 4-5 minutes. Add potatoes back in, stir to combine and set aside to cool slightly. Season to taste with salt.

Preheat oven to 425°F. Get a small bowl of water ready. Scoop a heaping teaspoon of the potato mixture into a dumpling wrapper. Dip a finger in the water and run it around the perimeter of the dumpling wrapper. Fold it in half and press the edges firmly to seal around the filling. Set on a baking sheet and repeat with remaining dumpling wrappers until you run out of wrappers or filling.

Brush each dumpling with a little extra peanut oil, and bake until golden brown, about 15-20 minutes.

While the dumplings are baking, prepare the peanut sauce. Heat peanut oil in a saucepan over medium heat. Add garlic and ginger and sauté until fragrant. Add remaining ingredients and whisk until smooth and heated through.