In a large bowl, combine beef, bread crumbs, salt, pepper, minced garlic, onion powder, and eggs. Form into 8-10 equal relatively flat patties. Heat a griddle to medium heat and cook patties until just cooked through, approximately seven minutes per side. Remove from the griddle and keep warm (I stick them on a plate and then in the microwave. Covering them with foil and placing them in the oven is a great idea too!)

Meanwhile, finely slice the mushrooms and onions. Heat a bit of olive oil over medium heat and add the onions. Cook for 4-5 minutes, until they start to soften. Then add the mushrooms. Feel free to season with a bit of salt and pepper and cook down until completely soft, about another 7 minutes. Remove from the pan.

In the same pan, melt butter. Stir in the flour and whisk until a light brown roux is formed. Gradually add the milk, whisking the entire time. Sprinkle in 1-2 teaspoons of beef broth base as you add the milk. Once the milk is incorporated, begin to stir in water, sprinkling in the remaining broth base to taste. Add pepper to taste. Whisk until a desired consistency is reached. Stir in cooked onions and mushrooms.

Finally, add the patties into the gravy to reheat just a bit. Serve, spooning additional gravy, mushrooms, and onions over the patties.