Lamb Ribs with Rhubarb and Radish Salad

Name: Lamb Ribs with Rhubarb and Radish Salad
Ingredients: 1 tablespoon black peppercorns; 1 tablespoon white peppercorns; 1 tablespoon coriander seeds; 1 tablespoon fennel seeds; 1 rack of Denver lamb ribs (about 2 pounds), outside fat trimmed to ½-inch thick; Kosher salt; 4 large rhubarb stalks (about 1 pound), cut into 1-inch pieces; ½ cup pure maple syrup; ¼ cup balsamic vinegar; ½ teaspoon finely grated lemon zest; 1½ teaspoons fresh lemon juice; ¾ teaspoon honey; ¾ teaspoon Dijon mustard; 2 tablespoons olive oil; Kosher salt and freshly ground black pepper; 1 bunch radishes, cut into matchsticks; 2 large rhubarb stalks (about 8 ounces), cut into matchsticks; 1 shallot, very thinly sliced; 1 cup mint leaves; A spice mill or a mortar and pestle