Savoury Sweet Potato Casserole

Bahan-bahan (10 porsi)

• 1.75 kg / 3.5lb sweet potato ((3 large or 6 smaller ones))
• 1/2 cup (115g) sour cream
• 1/2 cup (50g) parmesan (, freshly grated)
• 2 g arlic cloves (, finely minced)
• 3/4 tsp salt
• 1/4 tsp black pepper
• 250 g / 8oz butter (, salted, cut into 2cm/1" cubes)
• 15 sage leaves ((Note 1))
• 3/4 cup panko breadcrumbs ((Note 2))
• 1/2 cup (50g) parmesan (, finely grated)
• 1/4 tsp each salt and pepper
• 150 g / 5oz bacon (, streaky, cooked until golden then finely chopped)