Line a large rimmed baking sheet with foil and place a cooling rack in it. Arrange the bacon on the rack and sprinkle evenly with the 1/4 cup of brown sugar.
Bake for about 20 to 25 minutes, or until the bacon is nicely browned and glazed with the brown sugar. Remove the bacon from the rack and transfer to a plate; set aside to cool. Discard the bacon drippings or save them for another use.
In a medium bowl, combine the mayonnaise, vinegar, vegetable oil, sugar, and salt and pepper, to taste. Set aside.
Cut the broccoli florets into small, bite-size pieces.
In a large serving bowl toss the broccoli florets with the chopped red onion and raisins. Add the chopped walnuts, if using.
Dice or crumble the candied bacon and toss with the broccoli mixture.
Refrigerate until serving time.
Store leftovers in the refrigerator for up to 3 days.
Notes
Taste the dressing before adding to the broccoli mixture. Use as much or as little as you like, and adjust the sugar if you like broccoli salad more or less sweet.