Simmer the potatoes in salted water (add about a teaspoon) until done, about 10 minutes. (While they cook you can do the other part, but set a timer!) When done, set them to drain in a colander.
Saute the onions until translucent. Then add the Serrano, garlic, ginger, and spices. Cook together for about 2 minutes.
Add the peas and cook until they warm up, about 3-4 minutes.
Once everything is ready, stir it together along with the lemon and cilantro. Let some of the potatoes get mushed to hold the filling together, while others stay firm and a bit chunky to give a bit of texture.
Taste and adjust seasoning–potatoes often call for a fair bit of salt, so more salt might be needed.
This is from a foodwishes recipe for "samosadillas." It's meant to be used as a quesadilla filling, and then the quesadillas get dipped in the "Yogurt with Cilantro and Lime" sauce listed under sauces.
I found it a bit messy as a filling–maybe I didn't squish enough of the potatoes? But it was really tasty! And it can be eaten however you like; as a quesadilla filling, or just over rice. The dipping sauce is also versatile.