1. Make the whipped feta
 Combine the feta and 3 tablespoons olive oil in a food processor and process until completely smooth, about 2 minutes.
2. Make the lamb burgers
 In a medium bowl combine the ground American Lamb, fresh herbs, garlic, kosher salt, and 1 tablespoon olive oil and mix well. Form into four 4 ounce patties. Grill over high heat until cooked through, about 2 to 3 minutes per side or until the internal temperature reaches 160°F. Remove the burgers from the grill and set aside.
3. Assembly:
 While the burgers rest, brush the tomatoes with the remaining olive oil and place on the grill. Grill until char marks appear and the tomato just starts to soften, about 2 minutes per side, depending on the heat of your grill. Grill the buns until toasted then spread the whipped feta on both halves. Add the lamb burger then top with a grilled tomato and fresh arugula.