In a medium skillet, cook bacon over medium heat until crisp. Remove bacon, and let drain on paper towels. Let cool. Using a sharp knife, finely chop bacon.
In a small saucepan, stir together preserves and vinegar over medium heat until well combined. Add bacon, and bring mixture to a rolling boil. Reduce heat to low; simmer for 5 to 6 minutes. Remove from heat.
Preheat oven to 350°. Line a rimmed baking sheet with parchment paper.
Fill each phyllo cup with 1½ teaspoons Brie. Top each with ½ teaspoon bacon mixture. Place tartlets 2 inches apart on prepared baking sheet.
Bake for 10 minutes. Serve warm or at room temperature.
Garnish with thyme, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/apricot-bacon-brie-phyllo-tartlets/