Preheat oven to 400°F.
In a large skillet, over medium-low heat, add olive oil, butter, onions, sugar and salt. Cook for 20-25 minutes, until onions are caramelized. Add garlic and sun dried tomatoes to onions and cook for 1-2 minutes; set aside and cool completely. Caramelized onions can be prepared a day in advance.
On a lightly floured surface, roll out puff pastry to a 12 inch square. Place onion mixture in the center and top with the wheel of brie. Brush the edges of the pastry with egg and fold over Brie, making sure to enclose Brie completely in dough. Press all seams together. Place on baking sheet, seam side down. Brush top and sides of the pastry with egg. Bake for 25 minutes or until golden brown. ;Bake ahead of time and warm in a 350°F oven for 10-15 minutes. Makes 12 servings.
Approximate Nutrient Analysis per serving :
220 calories, 16 g fat, 5 g saturated fat, 35 mg cholesterol, 250 mg sodium, 14 g carbohydrate, 1 g fiber, 2 g sugar, 7 g protein