Preheat the oven to 400 degrees. Set the puff pastry on the counter so it can thaw.
In a large skillet, heat a tablespoon of oil. Add cumin seeds and cook until they sizzle. Add peas and cook covered for about 8-10 minutes until peas are softened.
Stir in the potatoes and cook another 5-10 minutes. Stir in ~2 tablespoons of coriander/mint chutney. Add salt to taste.
Taste the mixture for spice and salt.
Whisk an egg with a pinch of salt.
Place puff pastry on a floured surface. Spoon the filling slightly off center lengthwise. Fold the left side over the filling and then the right. Brush a little egg on top before baking.
Bake for about 18-20 minutes or until golden on a greased cookie tray. Sprinkle with chat masala as soon as the samosa loaf comes out of the oven. Serve with the coriander/mint chutney and ketchup