Place the tripe in a large covered pan and fill it with water to cover the tripe. Add the milk and the stalk of mint. Cover the pan slightly and cook over low-medium heat for about one hour until the tripe is very soft. Drain and let cool. Cut into small squares and reserve.
In a frying pan heat the oil, add the onion and cook until translucent. Add the garlic, the cumin, the aji (chile pepper), the turmeric, and stir until well combined and cooked through. Season to taste with salt and pepper.
Stir in the cut tripe and the cooked potato chunks and bring the mixture to a simmer. Add the lemon juice and the chopped fresh mint; stir to combine well.
Serve accompanied by rice.
Note: if desired, substitute chicken for the tripe.