Preheat your Traeger grill to 275 degrees Fahrenheit, but since you are using a pressure cooker, set it up according to your cooker's manual for beef roast recipes first.
Season the 3-pound beef chuck roast with salt, black pepper, and garlic powder all over.
Heat avocado oil or beef tallow in a cast iron skillet over medium-high heat. Sear the roast on all sides for about 3 to 4 minutes until a brown crust forms.
Slice the white onion thin and mince the garlic cloves.
Mix gochujang paste, red miso paste, sriracha, and garlic chili sauce in a bowl until smooth and thick.
Put the seared roast into the pressure cooker pot. Pour the spicy sauce over it, then layer the onions, garlic, and dried chili peppers on top. Add 2 cups of water.
Lock the lid and bring pressure up until the float valve pops up. Cook on high pressure for about 50 minutes, then use a slow release.
Let the roast rest for 10 minutes after cooking, then remove, shred or slice it, and scoop up the broth to pour over the meat.
If you don't have beef tallow, you can substitute with avocado oil or another cooking oil.
You can prep the sauce mix the day before to save time when ready to cook.
For a firmer beef texture, pressure cook for 40 minutes and adjust slow release time accordingly.
Notes
Serve immediately after shredding or slicing the roast to enjoy the tender, juicy flavors infused with Korean spices.