Preheat oven to 375°F (191°C). Lightly grease a 9 x 13-inch casserole dish with butter. Set aside.
Peel the yams, and slice them into ½-inch “coins” or “discs”. Evenly layer the yams into the greased casserole dish, overlapping the slices as necessary.
In a medium heavy-bottomed saucepan, over medium heat, combine 1 cup (217g) of the Redpath® Dark Brown Sugar, ½ cup (113g) cubed butter, pineapple juice, grated ginger, salt, pepper, cinnamon, nutmeg, and cloves. Stir to melt the butter and dissolve the sugar. Once sugar has completely melted, allow the sauce to simmer for 2 to 3 minutes without stirring. Remove from heat and stir in the vanilla extract.
With a ladle, spoon the sauce over the sliced yams, making sure all the yams are coated in the sauce.
Tightly cover the casserole with aluminum foil. With a skewer, poke a hole in each corner and poke a few holes down the centre of the foil to allow some of the steam to escape.
Place casserole into the preheated oven. At 20-minute intervals, uncover and flip the yam slices around to evenly distribute the sauce. Baste the slices with the sauce, cover and repeat until yams are tender; about 1 hour. When yams are tender, remove the casserole dish from the oven.
Set the oven to broil (leaving the rack in the centre position).
Uncover the dish, and dot the surface of the yams with the remaining 2 tablespoons (28g) of butter. Evenly sprinkle the surface of the yams with the remaining ½ cup (109g) Redpath Dark Brown Sugar and place back into the oven. Rotate the dish to evenly melt and caramelize the sugar; about 3 to 5 minutes.
Remove from oven and garnish with fresh thyme. Allow the casserole to cool slightly to thicken the sauce before serving; 10 minutes.