For the samosas: Preheat the oven to 375 degrees F. Line 2 baking sheets with parchment paper.
Heat the oil in a medium saute pan over medium-high heat until shimmering, about 2 minutes. Add the onions and chiles and season with salt and pepper. Cook until golden and fragrant, 4 to 5 minutes. Fold into the mashed potatoes, peas and coconut and set aside.
Cut the empanada discs in half. Take a half circle of dough and dampen the cut edge lightly with water, overlapping the cut edge with itself and sealing to making a cone. Fill the cone with 2 tablespoons filling. Dampen the open edge lightly with water and overlap the edges to seal shut. Repeat with the remaining dough and filling.
Set the samosas on the prepared baking sheet and bake until golden brown at the corners and a bit bubbly looking, about 25 minutes, rotating halfway.
For the raita: Season the cucumber with 1 teaspoon salt and let drain in a mesh strainer or on some paper towels for about 10 minutes. Squeeze out the excess liquid. Fold the cucumber, yogurt, ginger and cayenne together. Serve with the samosas.
Preheat the oven to 350 degrees F.
Roast the whole sweet potatoes on a baking sheet until tender, about 1 hour. Let cool for 10 minutes, then halve lengthwise and scoop out the flesh into a bowl. Mash to an even consistency. Season with salt and pepper.
Heat the clarified butter in a small saucepan over medium-high heat until shimmering, about 2 minutes. Add the coriander seeds, cumin seeds, mustard seeds, turmeric and curry leaves if using and shake the pan over the heat, taking care as the spices sizzle and pop. Remove from the heat once the spices become fragrant, about 1 minute. Pour over the sweet potatoes and fold in the cilantro and lime juice. Serve hot.