Preheat oven to 350 degrees Fahrenheit. Line a baking pan with Gefen Parchment Paper and set aside. Whisk together all the sauce ingredients in a small bowl until smooth.

Combine ground beef, egg, bread crumbs, and two thirds of the sauce in a large bowl. Stir until combined. Form the mixture into one-inch (two-centimeter) meatballs.

Place a small amount (about 1/4 teaspoon) of sauce in the bottom of each tart shell. Place a meatball into each tart, then brush sauce over the top.

Bake for 20 minutes, then brush more sauce over each tart. Broil for two minutes.