Pre-heat oven to 325°F.
Heat skillet over medium-low heat. Add butter, onion, salt, and pepper. Cook for 2 minutes till onions start to soften.
Add sugar to onions and cook for 10 minutes. Stir as the onion darken and caramelize. Add the broth, sherry, cream cheese, and ¼ cup for shredded cheese. Cook for 2 minutes, stirring, and allow the cheeses to melt.
Add about a tablespoon of filling to each tartlet. Top each tartlet with remaining shredded cheese, a sprinkle of bread crumbs, and dried parsley.
Place tartlets on a baking sheet and bake for 10-11 minutes. Serve immediately.