Place the bacon in a large, deep skillet, and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain the bacon slices on a paper towel-lined plate, let cool, and crumble the bacon.
Place the cream cheese, Cheddar cheese, and Dijon mustard into a bowl, and mix on medium speed with an electric mixer until the ingredients are thoroughly blended. Stir in the onion and crumbled bacon, and spoon into a serving bowl. Refrigerate for 2 hours to blend the flavors, and sprinkle with parsley to serve.