Super Easy Beef Stroganoff

I was served this dish soo often as a child that I often forget how delicious and festive a dish this makes. It's Baby Bee's new favorite, and Mr.Bee's all-time favorite, hence I make it often.

Ingredients:
2 cups heavy cream
1 small onion
4 cloves garlic
1 c beef stock
salt
pepper
oregano
5 tbsp butter
1 cup mushrooms, sliced
2.5 pounds beef brisket

Boil beef with half the onion and water until very tender. (About 2 hours on medium heat) In a saucepan, sautee in butter, the garlic and onions. Add cream and season with oregano, salt and pepper. Add 1 cup of the beef broth as well as the already tender beef, cut into strips. Simmer and add mushrooms. Serve on top of fetuccini.