Optional, for potatoes: butter, cream/milk, salt and pepper
Trim large chunks of fat from the pork roast. Season roast with salt and pepper. Heat olive oil in a large skillet over medium-high heat and brown the roast on all sides (about 2 minutes per side). If your slow cooker has a browning function, use that.
Place roast in the slow cooker and pour verde salsa all around. Cover and cook on low for 8-10 hours (recommended) or high 4-6 hours. Shred the meat in the slow cooker. Peel the potatoes and cut into large chunks each. Then place them in the slow cooker, making sure that they are at least partly submerged in the liquid. Replace the lid and turn the machine to high if it isn't already. Cook for another hour.
Remove the potatoes from the pot and transfer to a serving bowl. Using a fork or a potato masher, mash the potatoes until smooth. Add butter, milk or sour cream to taste if desired.
Serve Chile verde over mashed potatoes with juices from the pot.
Storing Leftovers: If you have leftovers, store the potatoes and meat separately or together in an airtight container for up to 3-4 days.Freezing: Cool chile verde and potatoes completely. Store in separate freezer safe containers or bags, squeezing out as much air as possible. Freeze for up to 6 months.Reheating: To reheat, thaw first if frozen, then reheat on the stovetop or in a slow cooker. You can also reheat individual portions in the microwave.