Tough beef stew meat in beef bourguignon
I used Ina Garten's beef bourguignon recipe. It calls for searing the meat on medium for 3-5 minutes, and then once the meat is added to the liquids and vegetables, bring it to a simmer. Then the pot is put into an oven at 250 degrees for 1.25 hours. Then you take the pot out to add a slurry, onions, mushrooms, and then bring the pot to a boil. Once, at boil, then you lower the heat and simmer for 15 minutes.
I followed these directions to a T, and the meat came out tough. I used beef chuck as she suggested. I also just recently read that you should not bring a beef stew to a boil, despite her recipe calling for it briefly.
How can I make the tough beef in this stew tender? Do I put in back in the oven for a few hours at 250 degrees, or do I simmer it on low on the stove for a few hours?