Boil the potatoes whole until tender. Remove from heat and drain. When cool enough to handle, slip the skins off the potatoes and cube or break into chunks. Set aside.

While the potatoes cook, prepare the rest of the ingredients. Heat the oil in a heavy skillet and add the mustard seed. After a minute or two, add the onion and sauté until softened, then add the ginger and green pepper and sauté 2 minutes. Stir in the turmeric and salt, then add the potatoes. Pour 1 cup of water into the skillet, stir well, and bring to a boil. Add the cliantro and lemon juice and remove from heat.

Place a heaping tablespoon of potato mixture on pita chips. Garnish with minced Serrano pepper and a dusting of garam masala. Serve immediately.