Preheat your oven to 400°F (200°C). In a small bowl, combine the melted butter, olive oil, chopped rosemary, salt, black pepper, and garlic powder. Stir well to create a flavorful mixture and set aside for later.

Peel the sweet potatoes, then thinly slice them evenly. Place the slices in a large bowl. Pour the reserved butter and olive oil herb mixture over the sweet potatoes, tossing to ensure all slices are coated. For extra flavor, you can swap the rosemary for thyme or another favorite herb.

Lightly spray a muffin pan with nonstick spray (or use a lined baking sheet if you prefer). Stack the coated sweet potato slices in layers in each muffin cup, trimming the slices as needed to fit. If the stacks are not stable, you can secure them with toothpicks on a baking sheet to prevent them from toppling over during baking. I like to really pack the stacks tightly for the best presentation.

Place the filled muffin pan (or baking sheet) in the preheated oven. Bake for about 30 minutes, or until the sweet potatoes are tender. Baking time may vary depending on the thickness of your slices and height of your stacks—check with a fork for doneness.

Remove the baked sweet potato stacks from the oven and let them cool slightly before serving. For a finishing touch, sprinkle them with a little extra flaky salt. I find that a final sprinkle of salt really brings out the sweetness of the potatoes.