Ingredients
Equipment
Method
- Heat olive oil in a large skillet over medium-high heat.
- Add the sliced red onion and cook for 5 minutes, stirring occasionally.
- Add the butter and sliced mushrooms to the skillet and continue cooking for 12-15 minutes, stirring frequently, until the mushrooms are tender and the onions are deeply caramelized and golden brown.
- Remove from heat and season with a pinch of salt and pepper. Keep warm while you cook the burgers.
- Preheat your grill to 450°F or heat a grill pan over medium-high heat.
- In a small bowl, combine salt, black pepper, garlic powder, onion powder, and dried rosemary to create the prime rib rub.
- Divide the ground beef into 4 equal portions and form into patties, each about 3/4-inch thick. Make a small thumb indentation in the center of each patty to prevent bulging during cooking.
- Coat both sides of each patty generously with the prime rib rub seasoning.
- Let the patties rest at room temperature for 20 minutes before grilling.
- Place the seasoned patties directly on the hot grill and cook for 3-5 minutes on the first side without moving them.
- Flip the patties once and cook for an additional 3 minutes on the second side.
- If using cheese, place a slice on top of each patty now, cover the grill, and cook for 1 additional minute until cheese begins to melt.
- Move the patties to the indirect heat (cooler side) of the grill for 1 minute to allow the cheese to fully melt.
- Toast the hamburger buns on the grill for about 1 minute until lightly golden.
- In a small bowl, mix together the light mayonnaise and BBQ sauce to create a BBQ aioli.
- Spread the BBQ aioli on the bottom bun of each burger.
- Layer lettuce, the cooked patty, caramelized mushrooms, and caramelized onions on each burger.
- Drizzle additional aioli on top if desired, then cap with the top bun.
- Serve immediately while still warm.
Nutrition
Notes
- Use 80/20, no substitutions — The fat-to-lean ratio is what keeps the patty juicy on a screaming-hot grill. Leaner blends dry out before they build a proper crust.
- Give the patties 20 minutes at room temp before grilling — Cold beef straight from the fridge cooks unevenly — charred outside, underdone center. Room temp rest closes that gap and gets the whole patty cooking at the same rate.
- Don't rush the onions — Real caramelized onions need 12 to 15 full minutes over medium-high heat. If they're still sharp and purple at 8 minutes, drop the heat and keep going. The sweetness is earned, not rushed.
- Press the thumb dent — Push a small indentation into the center of each raw patty. Burgers puff in the middle as they cook. The dent keeps them flat so the patty sits even and cooks consistently top to bottom.
- Pull at 160°F — Use a thermometer. Visual cues on ground beef are unreliable. 160°F internal is the target for food safety — don't guess.
- Build the aioli while the patties rest — Mix the mayo and BBQ sauce before you light the grill. Have it ready at assembly so you're not scrambling when the burgers come off.
- Crispy fries are the right call here. Thin, salted hard. Sweet potato fries work too and hold up well against the sweetness of the caramelized onions without getting lost.
- A sharp vinegar-based coleslaw cuts through the fat better than a creamy one. The acid does work here that a soft side can't.
- Pour a cold IPA or amber ale alongside. An IPA's bitterness stands up to the char and the beef fat. An amber's malt echoes the sweetness in the onions. Either works — neither is wrong.
- Throw a pickle spear on the plate. The acid resets the palate after each bite.
- Serve the finished burgers immediately. Once assembled, the bun softens fast and the beef dries out on reheat.
- The mushroom and onion mixture holds for up to one day in the refrigerator. Reheat gently in a skillet over low heat with a small knob of butter or a splash of water. Don't microwave it — the mushrooms go rubbery.
- Raw patties can be formed up to 4 hours ahead and kept covered in the refrigerator. Pull them out 20 minutes before you grill so they come up to room temperature before they hit the heat.