Wash the sweet potatoes thoroughly. You can choose to peel them or keep the skin on, according to your preference. Cut each sweet potato into 1/2-inch thick rounds, making sure the slices are as even as possible so they cook uniformly.

Preheat your oven to 200°C (400°F). In a large bowl or ziplock bag, combine the sliced sweet potatoes with the melted butter, 1 teaspoon ground cinnamon, salt, and black pepper. Toss or shake well so that all pieces are evenly coated with the mixture. I like to use my hands here to ensure every slice is well covered.

Arrange the seasoned sweet potato slices in a single layer on a baking tray, leaving a little space between each slice to ensure browning rather than steaming. Bake in the preheated oven for 25-30 minutes, or until the sweet potatoes are fork-tender. The baking time may vary depending on the thickness of your slices.

While the sweet potatoes are baking, mix together the chopped walnuts, 2 tablespoons maple syrup, 1/2 teaspoon ground cinnamon, and dried thyme in a small bowl. Stir well until the walnuts are fully coated in the syrup and spices. For extra flavor, I sometimes lightly toast the walnuts before mixing them with the syrup.

Remove the baking tray from the oven once the sweet potatoes are tender. Spoon about 1 teaspoon of the maple-walnut mixture onto each sweet potato slice, spreading it evenly. Return the tray to the oven and bake for another 8-10 minutes until the topping caramelizes and the edges of the sweet potatoes become slightly crisp and golden.

Once the sweet potatoes are caramelized, remove the tray from the oven and let them cool slightly before serving. Arrange them on a platter and serve as is, or sprinkle a little feta cheese over the top for a tangy contrast. I like to drizzle a little extra pure maple syrup on top just before serving for extra sweetness.