Season roast all over with salt and pepper. Place in a large slow cooker, along with pepperoncini and brine. In a small bowl, stir together soup mix, garlic powder, thyme and 1/2 cup water. Pour over roast. Dot the top of roast with butter. Cover and cook on low 8 to 9 hours, until tender.
Heat mashed potatoes according to package directions. To serve, transfer beef to a large bowl and shred, discarding any excess fat. Whisk mayonnaise into cooking liquid. Serve beef over mashed potatoes with pepperoncini and some cooking liquid.
Source: Hannaford fresh Magazine, January February 2024