2) Add the potatoes to a large pan and cover with salted water. Cook the potatoes over a medium-low heat until fork tender, about 8 to 10 minutes. When tender, drain and return the potatoes to the pan. Add the soured cream, milk, butter, pepper Jack, salt, pepper and the diced peppers.
3) Mash by hand with a potato masher and adjust the seasoning, if needed. Keep warm until ready to serve. Transfer to a serving bowl and garnish with coriander and cotija, if desired.