You could call this dish twice-baked yams: I add a couple of easy steps to upgrade the recipe from your typical candied yams. The cooking can be started the day before and finished the day of. It's really simple and extremely tasty with the addition of warm spices.
Preheat the oven to 350 F. Trim the ends of the yams. Rub the yams with a little olive oil and season with salt and pepper. Place the yams on a rimmed baking sheet and roast until completely soft and cooked through, about 40 to 60 minutes.
Remove the yams from the oven. Let them cool to room temperature; then place them in the refrigerator overnight.
Remove the yams from the refrigerator and cut them into 3/4-inch slices. Heat a large nonstick sauté pan over medium-high heat. Drizzle the remaining olive oil into the pan. While the oil is heating, season the sliced yams on one side with salt, pepper, and half the garam masala.
Lay the yams in the pan in a single layer, seasoned side down. Season the other side of the yams with salt, pepper, and additional garam masala. Using a fork, turn the yams over and continue to brown the other side. Remove the browned yams to a rimmed baking dish. Repeat with the remaining slices.
Preheat the oven to 425 F. Drizzle the maple syrup over the browned yams, and dot with the butter. Bake the yams for 10—15 minutes.
Remove the yams from the oven and serve immediately.