Melt butter in a
saucepan and add the flour. Whisk until smooth and cook on medium heat for 3-4 minutes, being careful to watch it so it doesn't burn. Add the cream, and keep whisking. As it thickens, keep adding more milk. Add the tomato paste, seasoning, and cream cheese – keep whisking it in as it melts. If this is done before you're ready to assemble, just turn your heat off and let set.