If you don't have cooked shredded beef, this is an idea for cooking your roast. For the shredded beef you can cook a 2 pound roast in your slow cooker. Place roast in slow cooker and add 1/2 cup water. Sprinkle a 1 ounce packet of onion soup mix over the roast. Then add 1 Tablespoon of Worcestershire sauce. You could also add in sliced onions and baby carrots if you would like some veggies to eat with your Chimichangas after the roast is done cooking. Low and slow is best. Low setting for about 5 hours. Check at 4 hours in case it doesn't take that long to cook.