Preheat the oven to 350°F.
Lightly grease a 9x13-inch baking dish with nonstick cooking spray.
In a medium bowl, whisk together the condensed cream of mushroom soup and whole milk until smooth.
Stir in the finely chopped fresh parsley.
Set the gravy mixture aside.
In a large mixing bowl, combine the ground beef, crushed saltine crackers, whole milk, Italian seasoning, garlic powder, onion powder, and cayenne.
Season the mixture with kosher salt and freshly ground black pepper to taste.
Using clean hands or two forks, gently mix the ingredients until just combined. Avoid overmixing, as this may result in firm patties.
Shape the beef mixture into evenly sized patties.
Place the all-purpose flour in a shallow dish.
Lightly dredge each patty in the flour, coating both sides.
Shake off any excess flour.
Heat a large skillet over medium-high heat.
Once the skillet is very hot, sear the patties on both sides until golden brown.
Work in batches if necessary to avoid overcrowding the skillet.
The patties do not need to be fully cooked at this stage, as they will finish baking in the oven.
Transfer the browned patties to the prepared baking dish.
Arrange the patties in a single layer.
Pour the mushroom gravy evenly over the patties.
Cover the baking dish with aluminum foil.
Bake for 30 to 40 minutes, or until the hamburger steaks are fully cooked through.
Remove the baking dish from the oven.
Allow the bake to rest for a few minutes before serving.
Serve warm with the gravy spooned over the patties.