Brie and Asparagus Phyllo Tarts

Ingredients (8)

• 24 prepared mini phyllo tart shells
• 1 wheel of brie cheese
• 1 tbsp butter
• 1 lb. asparagus
• 1 tbsp olive oil
• 1 medium sweet onion
• 1 tbsp brown sugar
• 1 tsp balsamic vinegar