Preheat the oven to 400 degrees F.
For the herb mixture: Put the whole peppercorns in a spice grinder and grind until coarse. Transfer to a small bowl and add the mint, rosemary, sage, thyme, oregano and garlic. Add the olive oil to the mixture and season with a pinch of salt.
For the lamb: Place the lamb racks on a work surface and sprinkle each side with 1 1/2 teaspoons of the salt. Rub the herb mixture on the lamb.
Heat a grill pan over high heat with some olive oil, add the racks rounded-side down and sear until brown, 3 to 5 minutes. Transfer to a rimmed baking sheet in the same position (do not flip). Roast until the desired doneness, 20 to 25 minutes for medium (about 145 degrees F). Let the lamb rest 5 to 7 minutes before slicing. Transfer the chops to a platter and serve with Apple-Mint Compote.
Put the sugar, corn syrup and 1/2 cup water in a medium heavy pot and bring to a boil. Add the apple and cook until thickened, about 10 minutes. Add the mint and vinegar and stir to combine. Season with salt.