Combine the lamb with the spinach, 3 tablespoons finely chopped mint, yogurt, garam masala, salt, pepper and garlic. Place about one-sixth of the mixture on a piece of wax or parchment paper and place another sheet on top. Roll out the meat into a thin free-form cutlet no more than 1/2-inch thick. Repeat for the remaining meat.
Combine the remaining mint with tomatoes, onions and some salt and pepper.
Heat the griddle to medium-high heat. Drizzle with some olive oil to lightly coat. Cook the patties until golden on each side, 6 to 8 minutes. Wipe the griddle and add a splash of water then add the naan bread, a few at a time, and cook until crispy and blistered on each side. Halve the naan across. Serve the patties on half a naan topped with some tomato salad and a dollop of yogurt, set another half of naan on top to complete your sandwich.
Get Rachael's shopping list for this episode's recipes here.