In a large pot, add the potatoes and cover them with water. Bring to a boil, then lower the heat and simmer the potatoes for 15-20 minutes until they are soft when pierced with a fork.
Drain the potatoes and run cold water over them to stop cooking.
Add the cooked potatoes, cumin, coriander, turmeric, garam masala, cayenne pepper, salt (if using), and lemon juice to a large bowl. Use a potato masher to mash the potatoes and combine the ingredients.
Add the peas to a colander and run hot water over them to thaw them.
Sprinkle 2 tablespoons of chickpea flour over the top and mix it into the potato mixture using a spoon or your hands.
Stir or knead in the thawed frozen peas, diced onions, jalapenos, ginger, garlic, and cilantro.
Check that the mixture is ready by forming a ball. If the ball crumbles apart, add more lemon juice. You need extra flour if the ball melts and spreads into your hand.
Use about ½ a cup of potato mixture to form about ½ an inch thick patties. Place the patties on a large tray or plate. Chill in the refrigerator for at least 30 minutes.
To bake, preheat the oven to 400 F (200 C). Line a baking sheet with parchment paper and carefully transfer the potato cakes to the tray.
Bake the potato cakes for 10-15 minutes until the top browns. Flip the patties and bake for another 10 minutes until golden brown and crispy.