Add 1/3 cup broth, the basil, parsley, pine nuts, parmesan cheese and lemon zest in a blender. Cover and blend until the mixture is smooth; set aside.
Combine the farro and remaining broth in a 2 1/2-quart saucepan; bring to a boil over high heat. Reduce the heat to low. Cover and cook for 15 minutes or until the farro is tender and the liquid is absorbed. Remove the farro to a large bowl and let cool for 30 minutes.
Thoroughly mix the lamb, half the garlic, feta and cumin in a large bowl. Season to taste with salt and pepper.
Shape the lamb mixture into 4 burgers. Insider Tip! To help keep the burgers from shrinking during cooking, use your thumb to make an indentation in the center of each burger.
Heat the oil in a 12-inch skillet over medium-high heat. To prevent sticking, make sure the skillet is hot before adding the burgers. Add the burgers and cook for 3 minutes; flip and cook for 3 minutes more.
Stir the yogurt, cucumber, mint, lemon juice and remaining garlic in a medium bowl. Season to taste.
Add the zucchini, corn, onion, blended broth mixture, lemon juice and salt to the cooled farro and toss to coat. Sprinkle with additional thinly sliced fresh basil, if desired.
Divide the burgers among the buns and layer with the yogurt mixture (mint tzatziki sauce), tomato, onion and arugula.
