Place cut potatoes in Instant Pot an add water until just covering potatoes. Cover with lid and pressure cook for 10 minutes.
Strain then mash potatoes and add remaining ingredients. Place mashed potatoes in another dish and set aside. Clean instant pot liner pot.
Next, heat Instant Pot to sauté mode (high) then add olive oil.
Add chuck roast and do not move it for 2 minutes (flipping to another side and repeating un-til all sides are seared).
Add beef broth, garlic cloves, and half amount of prepared onion. Place rosemary sprigs on top of chuck roast, cover with lid and set to pressure cook mode for 1hour 30 minutes. Once finished, manually release pressure.
Add prepared veggies, cover with lid, and pressure cook for 1 minute.
Next, discard rosemary sprigs and remove veggies and chuck roast form Instant Pot. Then, using two forks, shred meat, set all aside.
Heat remaining liquid on sauté mode. To a small bowl, combine arrowroot powder and water to make a slurry. Pour into remaining liquid, stirring often until thickened. Turn off heat. Set Aside.
Serve, store, and enjoy!
Notes
*You can reduce the amount of butter from 4 tbsp. to 2 tbsp. and use unsweetened almond milk in place of oat milk to reduce the overall calories.