Place the mushrooms in your food processor and process until finely ground. Add parsley and grind until fine.

Place chicken in a bowl. Add ground mushrooms and remaining ingredients. Form into patties.

Preheat grill until very hot. Grill on both sides until middle is done — about four minutes on each side.

To serve, slice open a multigrain bun. Smear a dollop of mayonnaise on the bottom of the bun, if desired. Add a generous amount of brisket sauce, the chicken burger, crispy lettuce, and some creamy coleslaw, if desired.