Oven Instructions:

1. Heat oven to 325° F and spray a glass 9×9 inch baking dish with non-stick cooking spray.
2. Heat a pan over medium high heat and add in the beef. Break it up. Add in the onion. Brown for 5 minutes. Drain off excess grease. Stir in the salt, pepper, garlic powder, yellow mustard and ketchup. Turn off stove and set aside.
3. In a bowl whisk together the milk, eggs and dry mustard. Add in the bread cubes, pickles, cheese, parsley and meat mixture. Stir until combined. Pour the mixture into the prepared pan.
4. Bake, uncovered, for 1 hour. 

Slow Cooker Instructions:

1. Spray the inside of your slow cooker with nonstick cooking spray.
2. Brown the beef and onion in a skillet on the stove. Drain off excess grease, then stir in the salt, pepper, garlic powder, mustard, and ketchup.
3. In a large bowl, whisk together the milk, eggs, and dry mustard. Add the bread cubes, pickles, cheese, parsley, and the cooked beef mixture, then stir until combined.
4. Pour the mixture into the slow cooker. Cover and cook on low for 4 hours or high for 2-3 hours or until the center is set and the eggs are cooked through. Let sit uncovered for about 10 minutes before scooping and serving.