Preheat the oven to 375F. Line a baking sheet with parchment paper.

In a large skillet, heat oil over medium-high heat.

Add onion and garlic and cook, stirring frequently until softened, about 5 minutes.

Stir in serranos, mustard seeds, cumin seeds and garam masala and cook, stirring, until fragrant, about 1 minute.

Stir in shrimp, mango and salt, and cook until shrimp are just cooked through, 4 to 5 minutes.

Remove from the heat, transfer to a bowl and stir in cilantro. Set aside to cool.

Remove dough from package in one piece and slice into 12 equal pieces.

On a lightly floured surface, roll each piece out into a circle about 4 inches in diameter.

Place a scant 1/4 cup of filling on the bottom half of each circle, fold top over filling and pinch edges to seal.

Place samosas on the baking sheet and press down on the sealed edges of each with the tines of a fork to crimp.

Pinch the rounded edge of each samosa into a point to make a triangle shape and sprinkle with cumin seeds.

Bake until dough is deeply browned, 15 to 17 minutes.

Cool 10 minutes before serving.