How to Make It
Heat the olive oil in a skillet over medium heat. Add the onion and sauté until soft and translucent, about 5 minutes. Transfer to a bowl and let cool.
Add the ground beef to the bowl and season with the tamarind, salt, and pepper, and knead well with your hands. Form balls the size of golf balls and refrigerate until ready to use.
Preheat the oven to 430°F. Line a baking sheet with parchment.
Spread the puff pastry on a floured work surface and cut into squares of about 2 inches. Brush with the egg and transfer to the baking sheet.
Place a meatball in the center of each pastry square. Flatten it slightly.
Bake for 20 minutes, or until golden. Serve warm or at room temperature.