Fire up grill and allow to come up to 450 degrees. Place olive oil in a small cast iron skillet on the grill. Add Vidalia onions and butter and allow to cook for 3-4 minutes, stirring often (shut top while not stirring to keep flame from getting out of control.) Add Portobello mushrooms and allow to cook for 4-5 minutes or until softening. Add balsamic and allow to cook for 3-4 minutes or until onions and mushrooms are soft and flavorful. Set aside.
Lightly mix ground beef, Worcestershire sauce and seasoning. Form into four 8 oz patties, then lightly press with your thumb in the middle of one side to help keep them even as they cook.
Oil grill to prevent sticking. Lightly sprinkle outside of burgers with burger seasoning, then place on medium hot grill. Allow to cook for 2-3 minutes, then rotate 90 degrees. Allow to cook for another 2-3 minutes, then flip and repeat (for a medium burger, adjust times for thickness and desired temperature.)
While burger is finishing, lightly toast buns on grill.
For the Brie
Large wheel of brie
½ TBS olive oil
Oil one side of the brie. Place oiled side down on a medium hot grill, but not over direct flame. Allow to grill for 2-3 minutes. Flip over into a prepared piece of foil, large enough to encircle the brie. Fold the foil over the sides of the brie, but not over the top. Score the top. As the brie gets melted, fold back rind to allow the brie to pick up some of the smoke flavor.
Place a small spoonful of the brie on the bottom of the bun. Place burger patty on bun, then top with Vidalia-portobello mix, then drizzle plenty of brie on top. Add your favorite fixings and enjoy!