Heat a large Dutch oven over medium high heat.
Cook bacon until crisp. Remove the bacon from the pan. Set aside.
Add the onions to the fat in the pan. Cook until onions are translucent and lightly browned, 10 to 15 minutes.
Add the bacon, mustard seeds, brown sugar, cider vinegar, red pepper flakes and balsamic vinegar. Stir to combine.
Bring to a simmer, then reduce heat and continue to cook until the liquid has reduced, about 45 minutes.
Remove from heat and let cool.
Spoon into jar and store in refrigerator.
Arrange cheeses and other items on cheese board. Serve with wine. Enjoy!