When it comes to browning the beef, you could use the SAUTÉ function of the Instant Pot, but I choose not to here for a few reasons:
1) Since this recipe uses 2 lbs of beef and the diameter of the Instant Pot insert is a little shy of 8 inches / 20 cm, you’d have to work in batches to get it all browned nicely. I find it much easier to throw everything into a large skillet than repeat the browning step multiple times in the Instant Pot, personally.
2) Stew beef gives off a lot of liquid that inhibits browning. Since we want both the flavor from the liquid, but also need a dry pan with plenty of fat to brown the beef, it’s easier to cook the beef in a large skillet, drain the liquid into the Instant Pot, then continue to brown and caramelize the beef in the skillet.
I’ve made this a few times and you can definitely tell when the pumpkin or butternut is left out: it adds a little extra savory flavor and helps to thicken things up a little. If you go for the larger amount of puree, then you may not want to thicken so much in the final step. Start with the smaller amount of arrowroot starch and then add extra if you think it’s needed.