Rhubarb Brie Burger

I grew up in Indiana, loving the rhubarb we enjoyed every summer. We made a rhubarb steak sauce that inspired me to get the taste into a burger !

Ingredients:

3 C chopped fresh or frozen rhubarb
1/2 tsp coarse ground mustard
1/4 C red wine vinegar
1/2 C diced onions
2/3 C brown sugar
1/4 tsp salt
1/4 tsp allspice
1 lb ground round ( coarse ground if possible)
1 lb ground sirloin
1 tsp kosher salt
1 tsp pepper
6 sesame buns, split
3 T softened butter

6 oz brie cheese, rind removed, cut into slices
6 romaine lettuce ( or your choice of lettuce)

Instructions:

Place rhubarb, mustard, vinegar, onions, sugar, 1/4 tsp salt and allspice into food processor. Process until finely chopped. Place the mixture into a grill-safe medium sized saucepan, but reserve 1/4 C of the mixture to mix into the beef. Cook the mixture over medium-high heat on grill until rhubarb and onions are soft and the mixture has thickened. You can remove the sauce and set aside.
While the sauce is cooking, place the ground round, sirloin, reserved 1/4 C chopped rhubarb mixture into a medium bowl and mix together. Form into 6 patties. Sprinkle with kosher salt and pepper on both sides. After you have removed the saucepan from grill,
place patties on medium-hot grill and cook for 3-4 minutes per side, turning once for medium doneness. Remove burgers , and cover with foil to rest as you prepare buns. Spread each bun with butter and grill until lightly toasted. To assemble: Spread a small smear
of the rhubarb sauce on tops and bottoms of buns. Place a lettuce leaf on each bun bottom. Top with warm burger. Place a slice of brie on top of each patty. Top the melting brie with a larger dollop of sauce, and cover with bun top. Serve extra sauce on the side for a little dipping if desired.