For the Instant Pot Version:

1. Cut excess fat off of roast. Then slice the roast into 2 inch slices across the grain. Coat the slices in the ranch dressing mix. Place the roast into the Instant Pot and pour in the beef broth. 
2. Cover Instant Pot and secure the lid. Make sure valve is set to sealing. Set the manual/pressure cook button to 50 minutes if making potatoes with the roast. At the end of 50 minutes perform a quick release and add in a steamer basket full of cubed potatoes on top of the roast. Cover the pot and set the manual/pressure cook button to 10 more minutes. At the end of the 10 minutes let the pot sit for a full natural pressure release up to 20-30 minutes. Then move the valve to venting and remove the lid.
3. Carefully remove the steamer basket and pour the potatoes into a large bowl. Mash the potatoes and add in butter and cream and salt and pepper to taste. 
4. Turn Instant Pot to the saute setting. Remove the pieces of meat and shred. Make the gravy by slowly whisking the gravy mix into the Instant Pot. If needed, add in a cornstarch slurry to thicken the gravy. Serve gravy over mashed potatoes and roast. 

For the Slow Cooker Version:

1. Cut excess fat off of roast. Then slice the roast into 2 inch slices across the grain. Coat the slices in the ranch dressing mix and brown gravy mix. Place the roast into the slow cooker and pour in the beef broth. 
2. Cover and cook on low for 4 hours then add in the potatoes and cook for another 2-3 hours, or until potatoes are tender. (Alternately you can add whole or halved potatoes in at the beginning of the cooking time).
3. Remove the potatoes with a slotted spoon and place in a bowl. Mash the potatoes and add in butter and cream and salt and pepper to taste. 
4. Remove the pieces of meat and shred. If needed, add in a cornstarch slurry to thicken the gravy. Serve gravy over mashed potatoes and roast.