Bring a pot of salted water to a boil. Cook the ravioli according to the package directions, 4 to 6 minutes. Reserve some of the pasta water, then drain the ravioli and set aside.
Put a large straight-sided skillet over medium-high heat and add the olive oil. When it begins to swirl, add the onions, a tiny pinch of salt and plenty of pepper and saute, stirring often, until the onions are golden on parts, about 5 minutes. Stir in the whipped cream cheese and mustard to combine, then slowly stir in the gravy. Bring to a simmer and cook, stirring occasionally, until the sauce is heated through and combined, about 5 minutes. Add some reserved pasta water if needed to reach the desired consistency.
Stir half of the parsley into the sauce, then pour the sauce over the pasta and garnish with the remaining parsley.