To make the onion jam:

• Heat the oil in a large frying pan over medium heat. Add onion. Cook, stirring occasionally, about 10 minutes or until softened. Add remaining ingredients & cook, uncovered, about 10 minutes, stirring occasionally, until jam is thickened – it will thicken further as it cools. 
• Place a piece of pork on a cutting board between two pieces of plastic wrap & pound with a meat mallet until about 1/4 inch thick. 
• Toss each pork piece in flour, then egg, then press into breadcrumbs. Cover & refrigerate until ready to use. 
  
• Heat a generous drizzle of oil in a large frying pan over medium heat. Cook pork in two batches, 3 to 4 minutes each side, until golden brown. Place on paper towel to drain. Then place in a single layer on a baking sheet. 
  
• Top each schnitzel with sliced Brie. Broil (grill) for 1 to 2 minutes or until melted & gooey.  
  
• Spread butter on both cut halves of each brioche. Brown in a large pan until golden & toasted. Spread a little onion jam on the bottoms of each bun. Top with schnitzel & melted Brie. Add a little more jam then top with lettuce leaves & top of buns. Secure with a skewer.