In a large bowl, combine ground beef and Burger Seasoning Blend.
Mix with hands to combine, being careful not to over-mix the beef.
Form beef into 9 patties, about 1/3 pound each.
Grill burgers on a medium high grill until the internal temperature reaches desired doneness, about 8-9 minutes for medium-well. (130 degrees for medium rare to 155 degrees for medium-well).
Top with cheese during the last minute of grilling.
Meanwhile, butter the inside of an onion roll and toast it in a buttered skillet until golden brown. Repeat for all of the remaining rolls.
Assemble burgers by placing cooked burger with cheese on the bottom half grill onion roll.
Top with prepared pierogi and caramelized onions.
Place top half of onion roll on the burger.
Repeat with remaining burgers.
Notes
Try Making it Hot: Try a Jalapeno pierogie with some Pepper Jack Cheese!
How about a Slider: Create your own Pierogie Burger sliders by using mini pierogies and slider rolls.
Get a little Messy: Add your favorite pizza sauce or my favorite boom boom sauce to make it extra flavorful.