A drizzle olive or canola oil
6 slices meaty bacon, chopped to finely chopped
2 onions, quartered and thinly sliced lengthwise
Salt and white pepper
A fat drizzle (about 1 tablespoon) aged Balsamic (such as Aged RR Balsamic)
Salt and coarse black pepper
1 1/2 pounds 80% lean ground sirloin
About 2 tablespoons Worcestershire sauce A handful of parsley, finely chopped
2 cloves garlic, peeled and grated or finely chopped
1/2 pound chunk crumbly smoked blue cheese or blue cheese (such as Oscar’s smoked blue), crumbled with a fork or your hands
4 potato hamburger rolls (such as Martin’s), lightly toasted
Trimmed watercress or Upland cress leaves
Heat a cast-iron skillet over medium to medium-high heat, add chopped bacon and render 2-3 minutes until lightly crispy. Remove to a paper towel-lined plate and reserve about 2 tablespoons bacon fat in pan.
Add onions to pan, lower heat and cook until light caramel in color, about 15-20 minutes, stirring frequently. (Add a splash of water if onions begin to brown.) Season with salt and white pepper. Finish onions with Balsamic vinegar. Remove the onions from the pan and wipe the pan clean.
While the onions cook, in a bowl combine beef, Worcestershire, parsley and garlic. Carefully mix in the bacon without overworking the meat. Score meat into 4 portions then form 4 patties that are thinner at center than edges for even cooking.
Return the clean pan to the heat with a drizzle of oil. Add patties and cook 4 minutes; turn and cook about 3 minutes more.
Build burgers: On the roll bottoms, place some cress, a patty, blue cheese crumbles mounded up a bit, some warm onions and the bun tops.