Place potatoes in 2-quart saucepan. Add water to cover. Bring to boil. Reduce heat to low; cover and simmer 10 minutes or until potatoes are tender. Drain and return to saucepan. Add 1/2 of the chickpeas, milk, butter and 1/2 teaspoon of the sea salt; coarsely mash until well blended. Set aside.
Preheat oven to 400°F. Brown lamb and beef in large nonstick skillet on medium-high heat. Drain fat. Add onion, cumin, coriander, remaining 1 teaspoon sea salt and pepper; cook 3 to 4 minutes or until onions are tender, stirring occasionally. Stir in whiskey. Stir beef stock into cornstarch until smooth. Add to skillet; stir constantly until well blended. Stir in vegetables and remaining chickpeas. Spoon into 2-quart baking dish. Spread potato mixture evenly over top.
Bake 15 to 20 minutes or until mixture is bubbly and top is golden brown. If needed, place under preheated broiler to brown potato topping.