Turkey burgers get a bad rap for being dry, but a healthy dose of Dijon-style mustard makes them both flavorful and moist. Grilled cherry tomatoes lend a juicy burst of sweetness. Serve burgers as open-face sandwiches with a big salad for a light but filling meal.
Soak four, 8- to12-inch bamboo skews in water for 30 minutes. Meanwhile, in a medium bowl combine 1 Tbsp. of the mustard, panko, milk, garlic, shallot, basil, and 1/4 tsp. each of the salt and pepper. Add ground turkey; mix well. Form into four 1/2-inch thick patties.
Thread cherry tomatoes on skewers. Brush lightly with olive oil.
For a charcoal or gas grill, grill burgers on the rack of a covered grill directly over medium heat for 11 to 13 minutes or until patties are done (165 degrees F), turning once halfway through grilling. Add the tomato skewers the last 6 minutes or grilling, turning to cook evenly.
Spread the cut sides of toasted bread with remaining Dijon mustard. Place each burger on top. Remove tomatoes from skewers and pile on the burgers. Drizzle with a little lemon juice and sprinkle with remaining salt and pepper. Top with basil.