Gourmet Bacon-Mushroom Cheeseburger

1 . Stage

Combine onion, bell peppers, and garlic in the bowl of a food processor; pulse until finely chopped but not quite pureed.

2 . Stage

Transfer onion mixture to a saute pan over medium heat; cook until reduced to a moist paste, about 20 minutes. When done, set aside to cool.

3 . Stage

Grate Cheddar and Asiago cheeses into a bowl using the finest teeth of a box grater.

4 . Stage

Place ground beef in a large mixing bowl. Add onion mixture and salt; mix thoroughly by hand until evenly combined. Add grated cheese mixture, a bit at a time, and mix until thoroughly combined. Add panko and mix until evenly distributed. Form into 8 balls and press into patties, using a hamburger maker if you have one. Wrap patties in waxed paper and refrigerate for at least 4 hours, but preferably overnight.

5 . Stage

Remove burgers from the refrigerator. Preheat an outdoor grill for 375 degrees F (190 degrees C) and lightly oil the grate.

6 . Stage

While the grill is preheating, cook bacon in a large skillet and over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain bacon slices on paper towels.

7 . Stage

Drain all but 1 tablespoon bacon grease from the skillet and add mushrooms. Saute over medium heat until soft, about 5 minutes. Set aside.

8 . Stage

Cook burgers on the preheated grill until no longer pink in the center, about 6 minutes per side. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C). During the last few minutes of cooling, add 2 slices bacon and 1 slice American cheese to each burger.

9 . Stage

Remove burgers from the grill. Place on Kaiser rolls and add mushrooms.