Mustard Onion Chuck Roast in Foil

8 servings borderline 6 or 7  
2 tbs. dry mustard
1 1/2 tsp. Water
3 pound beef chuck pot roast
2 medium onions, chunked
1/2 cup soy sauce  

Blend mustard and water to make a paste; let stand for 5 minutes. Place a large enough piece of foil to cover meat in a shallow baking pan; place meat on foil. Sprinkle onion pieces on meat. Stir 1 tbsp. soy sauce into mustard mixture, blending until smooth; stir in remaining soy sauce. Pour mixture evenly over beef and onions. Fold foil over meat; seal securely. Roast at 325 for 3 hours. Remove from oven, slice across grain, and serve with meat juices..... Throw it in at 3, it's ready at 6.  IF DONE IN CROCKPOT, COOK 6 to 8 HOURS on LOW.  Don’t life lid during cooking.  I do not use the foil in the crockpot --- just put it in all together.