Heat the olive oil in a pan and add the sliced onions. Cook for about 10 minutes and the onions become soft.
Add the balsamic, red wine and maple syrup. Cook for 30 minutes and the liquid has reduced to a syrup consistency.
Meanwhile press both sides of the bacon slices in the crushed walnuts and place on a baking sheet. Bake in a preheated 375 degrees oven for 15 minutes and the bacon is crispy around the edges.
Preheat your grill to a high heat and cook the beef patties, about 5 minutes on each side for medium-well done.
Slice the pear into 4 good size slices and grill for about 1 minute on each side.
Place some of the relish on the bottom of the bun followed by a beef patty.
Add two slices of the grilled pear, 2 slices of the walnut bacon and then the blue cheese.
Finally add some of the arugula and place the top of the brioche bun on the burger.