In skillet over medium-high heat, melt butter. Add onions, salt and pepper; cook until onions brown. Add sherry; bring to boil. Reduce heat and simmer until liquid evaporates, about 10 minutes. Stir in pecans.
On baking sheet, place filo pastry; top with brie. On top of brie, spread jelly. Brush filo edges with butter; roll edges over sides of brie, leaving top bare. Place onion mixture on top of brie. Bake in 350 F [180 C] oven until pastry is golden, about 15 minutes. Serve warm.
For decoration, tie green onion around center of brie bundle.