Heat oil in skillet and add the onions. Cover and cook on medium-low heat for 15 minutes, stirring occasionally.
Add the Chicken stock, balsamic vinegar and the sugar and salt. Cover and cook on medium-low heat for 25 to 30 minutes, stirring occasionally.
Put onion jam in a small bowl and set aside to cool. Onion jam can be made a day ahead and stored in the refrigerator.
Preheat oven to 400. Set pie tarts in an oven safe dish or on a cookie sheet.
Add a tablespoon of the cheese to each tart shell. Next divide the onion jam between the shells. Top with another Tablespoon of cheese. (Press mixture down if needed.)
In a small bowl add the half and half and the egg and beat together. Divide the mixture between the shells carefully. Bake for 25 minutes or until set.
Remove from oven and set aside. Next in a small bowl add four Tablespoons of the bacon bread crumbs and melted butter and mix together. Top each tart with a thin slice of tomato, then divide the bread crumb mixture between the tarts. Bake another five minutes, lowering the oven to 350.
seal the rest of the cheddar jack and bacon package up and save for later use on chicken or pork chops!