Chunky Shepherds Pie with Panko Parmesan Crust

Name: Chunky Shepherd's Pie with Panko Parmesan Crust
Ingredients: 2 pounds ground beef; kosher salt & freshly ground black pepper; 1 tablespoon butter; 1 tablespoon olive oil; 1 leek, washed well, sliced into half moons; 1 large yellow onion, chopped; 3 medium carrots, chopped; 2 celery stalks, chopped; 2 cloves garlic, minced; 1 6 ounce can tomato paste; 1 cup red wine (I used a malbec, any full bodied wine will work); 1 1/2 cups beef stock; 2 tablespoons worcestershire sauce; 6 sprigs thyme; 1 bay leaf; 1 cup frozen peas; 8-10 cups mashed potatoes; 1/4 cup grated parmesan cheese; 1/4 cup panko breadcrumbs