Bring chuck roast to room temperature at least 30 minutes prior to cooking, and generously coat with salt and pepper.
When it's time to cook, turn on Saute function on the Instant Pot and warm the oil in the inner pot.
Sear both sides of the chuck roast until golden brown, about 3-5 minutes each side, and remove from the pot. Select Cancel on the Instant Pot and add the removable trivet to the pot. Then add the meat and onions back into the pot.
Meanwhile, in a medium bowl whisk together the cocoa powder, red wine or broth, rosemary, garlic, Chipotle and tomatoes.
Pour the sauce mixture over the meat, and cover and lock the pot.
Select Manual High Pressure and set the time to 60 minutes if using 2 smaller pieces, or 75 minutes if using 1 large piece.
When complete, use a Quick release to release pressure from the pot, then remove the roast and set aside.