Place the potatoes in a pot of heavily salted water (salted like the sea as you would with pasta) and bring to a boil over medium high heat. Reduce the heat to medium and cook, uncovered, until the potatoes are tender, about 15–20 minutes. Add the frozen peas and continue to cook for another 2 minutes. Drain well, transfer to a large bowl and let cool to room temperature.
While the potatoes and peas are cooling, make the cilantro mint chutney. Combine all the ingredients in a blender and purée until smooth. If the mixture is too thick, add a tablespoon of water at a time until you reach a silky, spoonable consistency. Taste and adjust seasonings, if necessary. Transfer to a bowl and set aside until ready to serve.
Gently mash the cooled potatoes with a fork or your hands, being careful not to mush the peas too much, until the potatoes have a smooth, yet rustic texture. Add the cilantro, chopped serrano, powdered chillies, cumin seeds, amchoor powder, salt, turmeric and fennel seeds to the potato pea mixture. Mix well, taste and adjust seasonings, if necessary. Add the cornstarch, mix well and divide the mixture into 8 portions.
To form and stuff the aloo tikki, take one portion of the spiced potato pea mixture and gently roll into a ball. (I find that it is easiest to form these with slightly damp hands.) Flatten the ball into a large disk, cradling it in the palm of your hand to create a cup. Take a generous tablespoon of grated cheese and tuck it in the center. Gently push the sides together so the cheese is fully encased by the spiced potato and then flatten into a disk about 2 1/2–3 inches in diameter. At this point, I like to jump to Step 6 and fry one tikki to make sure that the cake will hold together.
If the aloo tikki holds together, repeat with the forming and filling process with the remaining 7 portions. If the tikki falls apart during cooking, remix the potato mixture with another tablespoon of cornstarch and then repeat the forming and filling process.
Pour about 1/2-inch canola oil into a large skillet and heat over medium high heat. When the oil is shimmering, add the potato cakes to the skillet and cook until deep golden brown and crisp on both sides, about 2–3 minutes per side. Transfer the cooked tikki to a paper towel-lined plate or baking sheet to drain off any excess oil.
Serve hot with the cilantro mint chutney on the side.
