Cook the ground beef in a skillet until no longer pink, drain, and add to the crock pot.
Melt the butter in the same skillet and sauté the onions and mushrooms for 3-5 minutes.
Add the flour and stir until the liquid combines with the flour.
Pour in the beef broth and stir until the flour is dissolved into the liquid.
Add in the worcestershire sauce, mustard, garlic powder, salt and pepper. Stir well.
Pour sauce over the meat in the crock pot.
Cook on low for 6 hours. You may want to eat it before that and that is fine.
Cook egg noodles according to the instructions on the package 10 minutes before you are ready to eat. Scoop the stroganoff mixture over a bed of noodles and enjoy!