1. In a small bowl, combine the mayonnaise, raisins, garlic and parsley. Season with salt and pepper.
2. Heat a large cast-iron skillet. Add the pine nuts and cook over low heat, stirring a few times, until well browned, about 5 minutes; let cool. In a large bowl, gently mix the ground buffalo with the pine nuts. Pat the meat into 4 burgers. Rub each burger with some of the soy sauce and season with salt and pepper.
3. In the skillet, heat the oil just until smoking. Add the burgers and cook over high heat until browned, crusty and rare, about 2 minutes per side. Serve the burgers on the buns with lettuce and the raisin-garlic mayonnaise.
Make Ahead: The mayonnaise can be refrigerated for up to 2 days.