Pulse cumin seeds, fennel seeds, ginger, and serrano peppers (if using) in a food processor until the spices are coarsely ground.
Heat oil in a skillet on medium heat. Add ground spices and fry for 20-30 seconds. Adjust the heat to prevent spices from burning.
Add thawed peas along with the garam masala to the skillet. Mix well with other spices. Cook peas with the spices for about five minutes. Mash a few peas while cooking so that the filling is easier to handle while stuffing the turnovers.
Add salt to taste and the lemon juice and mix well.
Turn the heat off. Let the mixture cool for a few minutes and then add chopped cilantro and mix well.
Preheat the oven to 350 F.
Remove the pie crust from the refrigerator and divide the dough equally into lime size balls.
Roll each ball to about 4” diameter circles. Use a little flour to make the rolling easier.
Fill each pastry round with one tablespoon of the peas mixture. Fold it over and pinch the edges with a fork or finger.
Place all turnovers on a parchment-lined baking tray.
Lightly brush all turnovers with the egg wash.
Bake for 20-30 minutes or until golden brown.
Remove from the oven and cool them down on a wire rack for a few minutes before serving.
You can make the turnovers ahead of time and store in the refrigerator for up to 3 days. To reheat them, place turnovers on a parchment-lined baking tray and heat in the oven at 350 F for five minutes.